Journal articles on the topic 'Multi channel analysis of surface waves MASW'

On May 27th 2006, Yogyakarta earthquake happened with 6.3 Mw. It was causing widespread destruction and loss of life and property. The average shear wave velocity to 30 m (Vs30) is useful parameter for classifying sites to predict their potential to amplify seismic shaking (Boore, 2004) [1]. Shear wave velocity is one of the most influential factors of the ground motion. The average shear wave velocity for the top 30 m of soil is referred to as Vs30. In this study, the Vs30 values were calculated by using multichannel analysis of surface waves (MASW) method. The Multichannel Analysis of Surface Waves (MASW) method was introduced by Park et al. (1999). Multi-channel Analysis of Surface Waves (MASW) is non-invasive method of estimating the shear-wave velocity profile. It utilizes the dispersive properties of Rayleigh waves for imaging the subsurface layers. MASW surveys can be divided into active and passive surveys. In active MASW method, surface waves can be easily generated by an impulsive source like a hammer, sledge hammer, weight drops, accelerated weight drops and explosive. Seismic measurements were carried out 44 locations in Yogyakarta province, in Indonesia. The dispersion data of the recorded Rayleigh waves were processed by using Seisimager software to obtain shear wave velocity profiles of the studied area. The average shear wave velocities of the soil obtained are ranging from 200 ms-1 to 988 ms-1, respectively.

The multi-channel analysis of surface waves (MASWs) method was used to obtain the shear wave velocity variations through near surface (depth < 30 m) and semi-deep (30 m < depth < 100 m) soil layers in the city of Ottawa, Canada. Sixteen sites were examined to evaluate the capability of the active and passive MASW methods for cases where the shear wave velocity(Vs)contrast between very loose soil (Vs< 200 m/s) and very firm bedrock (Vs> 2,300 m/s) is very large. The MASW velocity results compared with those of other geophysical approaches, such as seismic reflection/refraction methods and borehole data, where available, mostly confirming the capability of the MASW method to distinguish the high shear wave velocity contrast in the study area. We have found that, of the inversion procedures of MASW data, the random search inversion technique provides better results than the analytical generalized inversion method.

An acoustic soil profiler, using a so-called the high-frequency multi-channel analysis of surface waves (HF-MASW) method, has been developed, which uses surface (Rayleigh) waves to measure soil profile in terms of the shear (S) wave velocity as a function of depth, up to a 2.5 m deep below the surface. Several practical techniques have been developed to enhance the HF-MASW method, including (1) a variable sensor spacing configuration, (2) the self-adaptive method, and (3) the phase-only signal processing. Fundamentally, the S-wave velocity is related to soil mechanical and hydrological properties through the principle of effective stress. Therefore, the measured two-dimensional S-wave velocity images reflect the temporal and spatial variations of soils due to weather effects, geological anomalies, and anthropologic activities. Several HF-MASW applications will be reported, including (1) near surface soil profiling, (2) a long-term-survey for studying weather and seasonal effects, (3) short-term monitoring rain fall events, (4) detecting fraigpan layers, and (5) a farmland compaction study. This acoustic soil profiler can be used for agricultural, environmental, civil engineering, and military applications.

Surface-wave dispersion analysis is widely used in civil engineering to infer a shear wave velocity model of the subsoil for a wide variety of applications. Combining with a example, multi-channel analysis of surface waves method (MASW) was discussed in this paper. The entire MASW's procedure of three steps: acquiring ground roll data in the field, processing the data to determine dispersion curve, and back calculation of the geologic parameters for different depths. Based upon all the research results by far, MASW method is an efficient methods because of its high accuracy that is achieved by both special field technique and data processing technique.

The study was to characterize the sub surface at Agere in Ekori, using seismic refraction method, multichannel analysis of surface waves technique and borehole intrusive technique. Data were collected using a 12channel seismograph and other accessories required for seismic refraction data collection. Software called seismicimager was used to examine the data. The primary wave velocity in the first layer varied from 690 m/s at 4.2 m to 96 m/s at 7.3 m. A Vp range of 315 m/s to 484 m/s at a depth of 2 m is present inside the layer and represents the organic soil constituents. A Vp range of 669 m/s to 1756 m/s represents loose sand (dry), loose made ground (rubble), landfill rubbish, disturbed soil, and clay landfill, all within a depth of 2.3 m to 12.1 m. In addition to the borehole intrusive method, multichannel analysis of surface wave (MASW) techniques was used to calculate the soil profile based on velocity. The source was a 7 kg sledge hammer, the detectors (receivers) were 24 units of 4.5 Hz geophones, and the recorder was a Terraloc Mark 8 ABEM. Seismicimager software was used for analysis. At Ajere 1 through 6, the MASW test configuration employed 5 m geophone spacing and a source offset distance of 5 m, while at Ajere 7, it used 1 m geophone spacing and a source offset distance of 2 m. Near the boreholes, all of the MASW test arrays were run. The trustworthy seismic data from Ajere 1 to 6 at depths of 0.7 m to 13.1 m and 4.7 m to 17 m. Based on SPT N values, the results showed that the shear wave velocities had been classified into three layers of soil: very soft, soft, and firm. The velocities below 164 m/s, between 164 and 190, and 190 m/s to 320 m/s were classified as these soil types. In the meantime, a drilling invasive technique based on SPT N value determines changes in the soil layer. Hard material shear wave velocity data was not provided. In conclusion, because of its non-destructive, non-invasive nature and relative speed of evaluation, the MASW technique has the potential to be adapted in soil study to complement intrusive technique.

Surface wave dispersion imaging approach is crucial for multi-channel analysis of surface wave (MASW). Because the resolution of inversed S-wave velocity and thickness of a layer are directly subjected to the resolution of imaged dispersion curve. The τ-p transform approach is an efficient and commonly used approach for Rayleigh wave dispersion curve imaging. However, the conventional τ-p transform approach was severely affected by waves amplitude. So, the energy peaks of f-v spectrum were mainly gathered in a narrow frequency range. In order to remedy this shortage, an improved τ-p transform approach was proposed by this paper. Comparison has been made between phase shift and improved τ-p transform approaches using both synthetic and in situ tested data. Result shows that the dispersion image transformed from proposed approach is superior to that either from conventionally τ-p transform or from phase shift approaches.

Abstract In Western-Atakent (İstanbul), population density is increasing day by day and settlement areas are expanding. Soil properties and landslide conditions of these expanding regions must be absolutely examined. In the geophysics, there are many methods used to investigate landslide risks and geotechnical structure. The most common geophysical methods used for this purpose are the Electrical resistivity tomography (ERT), Multi-channel Analysis of Surface Waves (MASW) and Microtremor Survey Method (MSM) methods. These methods are very successful techniques for defining underground layers as geological structures, stratigraphic elements, soil layer thickness and landslide. Because of that reason in this study, soil properties and possibility of landslides of the Western-Atakent (İstanbul) region were investigated by using ERT, MASW, MSM and drilling methods. In this study the first stage, electrical resistivity data have been measured using dipole-dipole method on two profiles for ERT. In the second stage, MASW measurements have been made at 25 points on 5 seismic profiles in the field. In the third stage, MSM measurements have been made to determine the fundamental period in the 5-measure station in the study area. In the fourth and final stage, 10-pieces boreholes with a depth of 20 m were drilled to reveal the lithological structure of the study area. As a result of the evaluation of all data, parts of the region that could form landslides were revealed.

Geophysical methods have a varying degree of potential for detailed characterization of landslides and their dynamics. In this study, the application of four well-established seismic-based geophysical techniques, namely Ambient Noise Interferometry (ANI), Horizontal to Vertical Spectral Ratio (HVSR), Multi-Channel Analysis of Surface Waves (MASW) and Nanoseismic Monitoring (NM), were considered to examine their suitability for landslide characterization and monitoring the effect of seasonal variation on slope mass. Furthermore, other methods such as Ground Penetrating Radar (GPR) and DC Resistivity through Electrical Resistivity Tomography (ERT) were also used for comparison purpose. The advantages and limitations of these multiple techniques were exemplified by a case study conducted on Sobradinho landslide in Brazil. The study revealed that the geophysical characterization of the landslide using traditional techniques (i.e., GPR, ERT and MASW) were successful in (i) the differentiation between landslide debris and other Quaternary deposits, and (ii) the delineation of the landslide sliding surface. However, the innovative seismic based techniques, particularly ambient noise based (HVSR and ANI) and emitted seismic based (NM), were not very effective for the dynamic monitoring of landslide, which might be attributed to the short-time duration of the data acquisition campaigns. The HVSR was also unsuccessful in landslide site characterization i.e., identification of geometry and sliding surface. In particular, there was no clear evidence of the light seasonal variations, which could have been potentially detected from the physical parameters during the (short-time) ambient noise and microseismic acquisition campaigns. Nevertheless, the experienced integration of these geophysical techniques may provide a promising tool for future applications.

Worldwide, slip on earthquake faults causes numerous disasters, resulting in large losses in human life and built structures. To minimize future losses associated with earthquakes along such faults, it is important to precisely locate the faults relative to the built environment and to determine the subsurface geometry of the faults. In Beijing, China, we used shallow-depth geophysical methods to evaluate the location and subsurface geometry of the Huangzhuang-Gaoliying fault (HGF), one of the principal tectonic faults of Beijing area. We used seismic reflection and refraction tomography, multi-channel analysis of surface waves (MASW), and paleoseismic trenching to characterize the north section of HGF near the Gaoliying section of Beijing. Our seismic images indicated that there are at least two strands of the HGF that are distributed over an approximately 200-m-wide zone. We identified a principal fault strand (F1) that is observed in all the seismic images, as well as in a paleoseismic trench. The F1 strikes approximately N49°E and dips southeastward at 70° to 75°. Over the past few years, surface ruptures have occurred along the HGF in several locations, but it is unclear if the surface ruptures were the result of tectonic slip on the HGF or were related to land subsidence along the fault.

In situ, laboratory, and geophysical tests are currently used in site characterization. These tests explore different parts of a site measuring different engineering properties at different resolutions or scales. The test results are then used to derive a design profile. In traditional approaches, the positions of boundaries between geological units are identified first, and the soil profile is divided into several layers. Constant engineering properties are assigned to each geological unit and the variabilities within each layer are ignored. To take the uncertainties into account, characteristic design values are assigned. There are no commonly accepted guidelines for choosing design values, however, which introduces additional subjective uncertainties. This paper proposes a probabilistic site characterization approach, based on Bayesian statistical methods, that allows a design profile involving uncertainty to be determined automatically. The derived soil profile is not modelled by uniform layers, but by random fields, which can be used directly in probabilistic analysis. The proposed approach is verified by a synthetic example, and further applied to a soft soil test site in Ballina, New South Wales, Australia, and compared with traditional approaches. The results show that by gradually incorporating more data into the Bayesian inversion, the uncertainty in the soil profile is greatly reduced.

Landslides, as one of the main problems in mountainous areas, are a challenging issue for modern geophysics. The triggers that cause these phenomena are diverse (including geological, geomorphological, and hydrological conditions, climatic factors, and earthquakes) and can occur in conjunction with each other. Human activity is also relevant, undoubtedly contributing to the intensification of landslide phenomena. One of these is the production of artificial snow on ski slopes. This paper presents a multimethod approach for imaging the landslide structure in Cisiec, in southwestern Poland, where such a situation occurs. In the presented work, the integration of remote sensing with multi-method geophysical imaging was used to visualize landslide zones, and to estimate ground motion. To verify the uncertainty of the obtained data, the combination of electrical resistivity tomography (ERT), multi-channel analysis of surface waves (MASW), and seismic refraction method (SRT) was supported by synthetic modeling. Using geophysical data with accurate GPS-based topography and a terrestrial laser scanning-based digital terrain model (DTM), it was possible to model the spatial variability and surface area of the landslide more precisely, as well as to estimate the velocity field in the nearest surface more accurately. The final result shows displacement up to 1 m on the ground surface visible on the DTM models, while the geophysical methods confirm the change in internal structure. The proposed methodology is fast, cost-effective, and can be used to image the structure of landslides, where the shallowest parts are usually complex and thus difficult to observe seismically.

This study assesses the variability of shear-wave ( VS) profile determinations for a suite of methods at six industrial sites. The methods include active, consisting of multi-channel analysis of surface waves (MASW), as well as passive, consisting of refraction microtremor (ReMi), and extended spatial autocorrelation (ESAC). The purpose is to ascertain the effect of the higher level of ambient noise on the results from the different methods, as only a few of these many methods are commonly used for site characterization. The measured dispersion curves are in fair agreement with one another. The average coefficient of variation (CoV; the percentage ratio of the standard deviation to the mean) for the dispersion curves varied from 2.5% to 12.6%. In contrast, over the VS-depth domain, the average shear-wave velocity profiles to a depth z ( VS,Z) vary from 11.6% to 16.5% between the various methods at the different sites. This indicates that the variance among the individual methods can lead to significant misinterpretation of the shallow subsurface, while the average VS,Z is much more robust. This reaffirms its use (mainly as VS,30) in building codes and within ground motion prediction equations (GMPEs). At all six sites, because of inversion processes, the variability within each method ranges from 4% up to 14%. There is no correlation between the test type and the CoV. Our study focused on surface-wave measurements in noisy industrial environments, where the signals processed are typically complex. Despite this complexity, our results suggest that such tests are also applicable to industrial zones, where the noisy environment constitutes an energy source.

Single-station microtremor measurements were conducted to investigate earthquake and soil behaviour for the first time in Nicosia, Cyprus. Cyprus is located in a tectonically complex area in the Eastern Mediterranean where three plates meet. The study area was chosen to cover the areas to be opened for new development. Nicosia, the capital of Cyprus, is also the island's most important cultural, industrial, commercial, and transportation centre. The study creates base maps for the soil to assess earthquake resistance crucial for construction. Microtremor Method was applied at 100 stations and the Multi-Channel Analysis of Surface Waves (MASW) method was used at 52 stations. Also, RefractionMicrotremor (Re-Mi) and L-Shaped Spatial Autocorrelation (L-SPAC) methods were carried out at 17 stations to substantiate the research. The results of the microtremor method indicate that the predominant soil period values have an average of 1 second and pre-dominant peak period values are generally found between 0.1 to 5 s at the study area. Peak amplitude values are observed between 1 and 2.4. The Vulnerability Index Parameter (Kg) exceeded 20 at the central and the southern stations, and Kg values change between 7 and 54 units. The Kg values were found to be higher than 20 in soils where shear wave velocity is lower than 760 m/s. At the same time, the values of the predominant peak period were greater than 1 second. Cyprus is located in the Alpine Himalayan earthquake zone. The Cyprus Arc is known as the main seismic source of the island, It constitutes the tectonic border among African and Eurasian lithospheric plates in the region. During an earthquake in Nicosia, seismic waves will be amplified by an average of 1.5 times and soil deformation will occur due to the exceeding elastic limits. The results provided important insight into soil behaviour and indicated its reactions in a potential earthquake.

The multichannel analysis of surface waves (MASW) seismic method was used to delineate a fault zone and gently dipping sedimentary bedrock at a site overlain by several meters of regolith. Seismic data were collected rapidly and inexpensively using a towed 30-channel land streamer and a rubberband-accelerated weight-drop seismic source. Data processed using the MASW method imaged the subsurface to a depth of about [Formula: see text] and allowed detection of the overburden, gross bedding features, and fault zone. The fault zone was characterized by a lower shear-wave velocity [Formula: see text] than the competent bedrock, consistent with a large-scale fault, secondary fractures, and in-situ weathering. The MASW 2D [Formula: see text] section was further interpreted to identify dipping beds consistent with local geologic mapping. Mapping of shallow-fault zones and dipping sedimentary rock substantially extends the applications of the MASW method.

Abstract We present a method that utilizes multichannel analysis of surface waves (MASW), which was used to measure shear wave velocities, with a view to establishing the probable causes of road failure, subsidence and weakening of structures in some local government areas in Lagos, Nigeria. MASW data were acquired using a 24-channel seismograph. The acquired data were processed and transformed into a two-dimensional (2-D) structure reflective of the depth and surface wave velocity distribution within a depth of 0–15 m beneath the surface using SURFSEIS software. The shear wave velocity data were compared with other geophysical/ borehole data that were acquired along the same profile. The comparison and correlation illustrate the accuracy and consistency of MASW-derived shear wave velocity profiles. Rigidity modulus and N-value were also generated. The study showed that the low velocity/ very low velocity data are reflective of organic clay/ peat materials and thus likely responsible for the failure, subsidence and weakening of structures within the study areas.

Assessment of roadway subsidence caused by embedded low-velocity anomalies is critical to the health and safety of the traveling public. Surface-based seismic techniques are often used to assess roadways because of data acquisition convenience and large depths of characterization. To mitigate the negative impact of closing a traffic lane under traditional seismic testing, a new test system that uses a land streamer is presented. The main advantages of the system are the elimination of the need to couple the geophones to the roadway, the use of only one source at the end of the geophone array, and the movement of the whole test system along the roadway quickly. For demonstration, experimental data were collected on asphalt pavement overlying a backfilled sinkhole that was experiencing further subsidence. For the study, a 24-channel land streamer and a propelled energy generator to generate seismic energy were used. The test system was pulled by a pickup truck along the roadway and the data were collected with 81 shots at every 3 m for a road segment of 277.5 m, with a total data acquisition time of about 1 h. The measured seismic data set was analyzed by the standard multichannel analysis of surface waves (MASW) and advanced two-dimensional (2-D) waveform tomography methods. Eighty-one one-dimensional shear wave velocity (VS) profiles from the MASW were combined to obtain a single 2-D profile. The waveform tomography method was able to characterize subsurface structures at a high resolution (1.5- × 1.5-m cells) along the test length to a depth of 22.5 m. Very low S-wave velocity was obtained at the repaired sinkhole location. The 2-D VS profiles from the MASW and waveform tomography methods are consistent. Both methods were able to delineate high- and low-velocity soil layers and variable bedrock.

The Multi-Channel Method for Surface Waves (MASW) was used to estimate the average velocity of shear waves in order to construct an engineering structure and its relationship to bearing capacity, foundation depth and soil thickness in this construct in the center of Hilla city. Active MASW was used in this study which allows us to measure the apparent dispersion curve or the phase velocity within the frequency range from 5 to 70 Hz, which gives information about the shallow layers (25-50 m) and depending on the ground hardness and spreading length. Where it was found that this area consists of two layers and each layer has a shear velocity, as the first layer has shear velocity (171.891) m/sec and the depth (8.244) m and the second layer has shear velocity (274.788) m/sec and the maximum bearing capacity value relative to the depth of the foundation is 1, 2 and 3 is 4.46, 5.27 and 5.96 T/m2 respectively. According to this study, this area is suitable for constructing an engineering structure on it.

Soil compaction plays an important role in every construction activities to reduce risks of any damage. Traditionally, methods of assessing compaction include field tests and invasive penetration tests for compacted areas have great limitations, which caused time-consuming in evaluating large areas. Thus, this study proposed the possibility of using non-invasive surface wave method like Multi-channel Analysis of Surface Wave (MASW) as a useful tool for assessing soil compaction. The aim of this study was to determine the shear wave velocity profiles and field density of compacted soils under varying compaction efforts by using MASW method. Pre and post compaction of MASW survey were conducted at Pauh Campus, UniMAP after applying rolling compaction with variation of passes (2, 6 and 10). Each seismic data was recorded by GEODE seismograph. Sand replacement test was conducted for each survey line to obtain the field density data. All seismic data were processed using SeisImager/SW software. The results show the shear wave velocity profiles increase with the number of passes from 0 to 6 passes, but decrease after 10 passes. This method could attract the interest of geotechnical community, as it can be an alternative tool to the standard test for assessing of soil compaction in the field operation.

Recent studies have illustrated that the Multichannel Analysis of Surface Waves (MASW) method is an effective geoacoustic parameter inversion tool. This particular tool employs the dispersion property of broadband Scholte-type surface wave signals, which propagate along the interface between the sea water and seafloor. It is of critical importance to establish the theoretical Scholte wave dispersion curve computation model. In this typical study, the stiffness matrix method is introduced to compute the phase speed of the Scholte wave in a layered ocean environment with an elastic bottom. By computing the phase velocity in environments with a typical complexly varying seabed, it is observed that the coupling phenomenon occurs among Scholte waves corresponding to the fundamental mode and the first higher-order mode for the model with a low shear-velocity layer. Afterwards, few differences are highlighted, which should be taken into consideration while applying the MASW method in the seabed. Finally, based on the ingeniously developed nonlinear Bayesian inversion theory, the seafloor shear wave velocity profile in the southern Yellow Sea of China is inverted by employing multi-order Scholte wave dispersion curves. These inversion results illustrate that the shear wave speed is below 700 m/s in the upper layers of bottom sediments. Due to the alternation of argillaceous layers and sandy layers in the experimental area, there are several low-shear-wave-velocity layers in the inversion profile.

A geophysical investigation was performed to evaluate the effectiveness of three geophysical methods (electrical resistivity imaging (ERI), seismic refraction (SR), and multiple-channel analysis of surface waves (MASW)) for geotechnical site characterization in swamps and environmentally sensitive wetland areas. The geophysical test results were verified against the results from borehole and cone penetrometer test logs. The ERI results were best for determining the depth to the glacial till. However, the resolution of the ERI survey was not sufficient to accurately predict the upper lithologies. The electrode spacing (4 m) was instead selected to reliably predict the depth to the till, which in this case varied between 4.6 and 10.7 m. The SR results overestimated the depth to the till because of the presence of a stiffness reversal. The MASW results predicted the depth to the refusal till layer less accurately than the ERI method. However, this method was able to detect the three distinct layers above the till, even though the layer thicknesses were consistently underestimated. The complementary use of geophysical techniques was a successful approach in determining the main soil units and the depth to the competent layer (till) at the site. These methods can be used as a basis for further development to optimize a procedure to reduce the number of boreholes required for conventional site investigations in areas that are environmentally sensitive or where access is restricted.

SUMMARY Ambient wavefield data acquired on existing (so-called ‘dark fibre’) optical fibre networks using distributed acoustic sensing (DAS) interrogators allow users to conduct a wide range of subsurface imaging and inversion experiments. In particular, recorded low-frequency (<2 Hz) surface-wave information holds the promise of providing constraints on the shear-wave velocity (VS) to depths exceeding 0.5 km. However, surface-wave analysis can be made challenging by a number of acquisition factors that affect the amplitudes of measured DAS waveforms. To illustrate these sensitivity challenges, we present a low-frequency ambient wavefield investigation using a DAS data set acquired on a crooked-line optical fibre array deployed in suburban Perth, Western Australia. We record storm-induced microseism energy generated at the nearby Indian Ocean shelf break and/or coastline in a low-frequency band (0.04−1.80 Hz) and generate high-quality virtual shot gathers (VSGs) through cross-correlation and cross-coherence interferometric analyses. The resulting VSG volumes clearly exhibit surface wave energy, though with significant along-line amplitude variations that are due to the combined effects of ambient source directivity, crooked-line acquisition geometry and the applied gauge length, fibre coupling, among other factors. We transform the observed VSGs into dispersion images using two different methods: phase shift and high-resolution linear Radon transform. These dispersion images are then used to estimate 1-D near-surface VS models using multichannel analysis of surface waves (MASW), which involves picking and inverting the estimated Rayleigh-wave dispersion curves using the particle-swarm optimization global optimization algorithm. The MASW inversion results, combined with nearby deep borehole information and 2-D elastic finite-difference modeling, show that low-frequency ambient DAS data constrain the VS model, including a low-velocity channel, to at least 0.5 km depth. Thus, this case study illustrates the potential of using DAS technology as a tool for undertaking large-scale surface wave analysis in urban geophysical and geotechnical investigations to depths exceeding 0.5 km.

Suppression of surface wave interference is a necessary step in the processing of land seismic data. Traditional methods, such as single-channel band-pass filtering and multi-channel FK filtering, often fail to separate the desired signal from interference. The proposed method of suppressing surface waves based on the analysis of the main components of the wave field in the time-frequency domain shows the best results. The method is based on the model of surface wave propagation in horizontally layered media, however, numerical experiments were carried out demonstrating the applicability of the method in horizontally heteronode three-dimensional media. A software package "PF Seism" has been developed and registered, which implements the proposed method for suppressing surface waves.

Abstract. Ice properties inferred from multi-polarization measurements, such as birefringence and crystal orientation fabric (COF), can provide insight into ice strain, viscosity, and ice flow. In 2008, the Center for Remote Sensing of Ice Sheets (CReSIS) used a ground-based VHF (very high frequency) radar to take multi-channel and multi-polarization measurements around the NEEM (North Greenland Eemian Ice Drilling) site. The system operated with 30 MHz bandwidth at a center frequency of 150 MHz. This paper describes the radar system, antenna configurations, data collection, and processing and analysis of this data set. Within the framework derived from uniaxial ice crystal model, we found that ice birefringence dominates the power variation patterns of co-polarization and cross-polarization measurements in the area of 100 km2 around the ice core site. The phase shift between ordinary and extraordinary waves increases nonlinearly with depth. The ice optic axis lies in planes that are close to the vertical plane and perpendicular or parallel to the ice divide depending on depth. The ice optic axis has an average tilt angle of about 11.6° vertically, and its plane may rotate either clockwise or counterclockwise by about 10° across the 100 km2 area, and at a specific location the plane may rotate slightly counterclockwise as depth increases. Comparisons between the radar observations, simulations, and ice core fabric data are in very good agreement. We calculated the effective colatitude at different depths by using azimuth and colatitude measurements of the c axis of ice crystals. We obtained an average effective c axis tilt angle of 9.6° from the vertical axis, very comparable to the average optic axis tilt angle estimated from radar polarization measurements. The comparisons give us confidence in applying this polarimetric radio echo sounding technique to infer profiles of ice fabric in locations where there are no ice core measurements.

Abstract. Several numerical experiments are performed in a nonlinear, multi-level periodic channel model centered on the equator with different zonally uniform background flows which resemble the South Equatorial Current (SEC). Analysis of the simulations focuses on identifying stability criteria for a continuously stratified fluid near the equator. A 90 m deep frontal layer is required to destabilize a zonally uniform, 10° wide, westward surface jet that is symmetric about the equator and has a maximum velocity of 100 cm/s. In this case, the phase velocity of the excited unstable waves is very similar to the phase speed of the Tropical Instability Waves (TIWs) observed in the eastern Pacific Ocean. The vertical scale of the baroclinic waves corresponds to the frontal layer depth and their phase speed increases as the vertical shear of the jet is doubled. When the westward surface parabolic jet is made asymmetric about the equator, in order to simulate more realistically the structure of the SEC in the eastern Pacific, two kinds of instability are generated. The oscillations that grow north of the equator have a baroclinic nature, while those generated on and very close to the equator have a barotropic nature. This study shows that the potential for baroclinic instability in the equatorial region can be as large as at mid-latitudes, if the tendency of isotherms to have a smaller slope for a given zonal velocity, when the Coriolis parameter vanishes, is compensated for by the wind effect.Key words. Oceanography: general (equatorial oceanography; numerical modeling) – Oceanography: physics (fronts and jets)

Cracks have been developed in a large lecture hall on the University of Mosul Campus. These cracks exist along two sides of the building. Multi Analysis Surface Wave and Electrical Resistivity Tomography surveys were conducted at the surrounding building to investigate the nature and distribution of shallow subsurface soil/rock. The MASW’s data show three layers: the first layer is characterized by low shear wave velocity ranges between 210 and 420 m/s which is attributed to infill materials, the next layer is attributed to a river terrace (fairly competent rock) which has Vs ranging from 430m/s to 840 m/s. It is recognized by a gradual increase in mechanical characteristics as depth increases. In-depth between about 2.5m and 6.0 m the shear wave velocity drops in the top contact of this layer. The causes of low velocity may be due to weathering of the medium because of a sinkhole. The Electrical Resistivity Tomography profile shows four electrical zones, the first zone has 50-70 Ω.m. with a variable thickness from 0.5-1.5 m which indicates infill materials. The second zone has very low resistivity value, and a depth ranges 0.5m - 3.5 m, which might be interpreted to be increased clay, silt and water content (high water-saturated zone). The third zone is characterized by a high-resistivity value (>100 Ω.m) that could be related to a dry conglomerate rock and gravels belong to river terraces. The fourth zone has a low-resistivity value (<20 Ω.m) associated with a water-saturated marl bed. We could be definitively correlated the resistivity and velocity anomalies to sinkhole activity in were identified and characterized using combined geophysical methods. The Multi Analysis Surface Waves and Electrical Resistivity Tomography were shown to complete each other in the evaluation. The variations in Vs (low velocity) and resistivity (conductive zone) within the river terrace were detected and proposed to be indicative of dissolution and the subsidence responsible for structural damage implied by the change in the velocity and resistivity. The roughness of the top terrace surface strongly influences the nature of the velocity and resistivity values. This roughness is suggestive of dissolution or erosion.

The analysis of seismic noise provides a reliable estimation of the soil properties, which supposes the starting point for the assessment of the seismic hazard. The horizontal-to-vertical spectral ratio technique calculates the resonant frequency of the soil just by using a single three-component sensor. Array measurements require at least several vertical sensors registering simultaneously and their analysis provides an estimation of the surface waves dispersion curve. Although these methods are relatively cheaper than other geotechnical techniques, the cost of the sensors and the multi-channel data acquisition system means that small research groups cannot afford this kind of equipment. In this work, two prototypes for registering seismic noise have been developed and implemented: a three-channel acquisition system, optimized for working with three-component sensors; and a twelve-channel acquisition system, prepared for working simultaneously with twelve vertical geophones. Both prototypes are characterized by being open-hardware, open-software, easy to implement, and low-cost. The main aim is to provide a data acquisition system that can be reproduced and applied by any research group. Both developed prototypes have been tested and compared with other commercial equipment, showing their suitability to register seismic noise and to estimate the soil characteristics.

We study the stability of the interface between (a) two adjacent viscous layers flowing due to gravity through an inclined or vertical channel that is confined between two parallel plane walls, and (b) two superimposed liquid films flowing down an inclined or vertical plane wall, in the limit of Stokes flow. In the case of channel flow, linear stability analysis predicts that, when the fluids are stably stratified, the flow is neutrally stable when the surface tension vanishes and the channel is vertical, and stable otherwise. This behaviour contrasts with that of the gravity-driven flow of two superimposed films flowing down an inclined plane, where an instability has been identified when the viscosity of the fluid next to the plane is less than that of the top fluid, even in the absence of fluid inertia. We investigate the nonlinear stages of the motion subject to finite-amplitude two-dimensional perturbations by numerical simulations based on boundary-integral methods. In both cases of channel and film flow, the mathematical formulation results in integral equations for the unknown interface and free-surface velocity. The properties of the integral equation for multi-film flow are investigated with reference to the feasibility of computing a solution by the method of successive substitutions, and a deflation strategy that allows an iterative procedure is developed. In the case of channel flow, the numerical simulations show that disturbances of sufficiently large amplitude may cause permanent deformation in which the interface folds or develops elongated fingers. The ratio of the viscosities and densities of the two fluids plays an important role in determining the morphology of the emerging interfacial patterns. Comparing the numerical results with the predictions of a model based on the lubrication approximation shows that the simplified approach can only describe a limited range of motions. In the case of film flow down an inclined plane, we develop a method for extracting the properties of the normal modes, including the ratio of the amplitudes of the free-surface and interfacial waves and their relative phase lag, from the results of a numerical simulation for small deformations. The numerical procedure employs an adaptation of Prony's method for fitting a signal described by a time series to a sum of complex exponentials; in the present case, the signal is identified with the cosine or sine Fourier coefficients of the interface and free-surface waves. Numerical simulations of the nonlinear motion confirm that the deformability of the free surface is necessary for the growth of small-amplitude perturbations, and show that the morphology of the interfacial patterns developing subject to finite-amplitude perturbations is qualitatively similar to that for channel flow.

Wireless underground sensor networks (WUSNs) are sub-ground-surface sensor node networks designed to establish real-time tracking capacities in diverse underground ecosystems composed of soil, water, oil, and other materials. The contact medium is the key distinction between USNs and terrestrial wireless sensor networks. The communication properties of electromagnetic (EM) waves in underwater resources like mud, water, oil, and other materials, as well as major variations between propagation in air, make classification of the underground wireless channel difficult. From the transmission of data, the channels modelling is involved to remove the noise and reduce the energy. After that Multi-driven Clustering Algorithm (MCA) method is used to cluster the channel based on the EDT method (Energy, Distance, and Time). Completing the transmission, the data can be transmitted to the destination. The experimental portion of the proposed method is analyzed by varying parameters such as energy, throughput, channel response, and time duration of the data transmission. From the experimental analysis, it is observed that 55% and 45% more energy levels can be saved with the proposed MCA method than with the LEACH methods for DR and SW media methods, respectively. The throughput of the proposed method is proven with 45% and 42% improvement over the time horizon in the median under the frequency for soil of the LEACH and LEACH-CO2 methods, correspondingly.

A large-scale field deployment of high-density, real-time wireless sensors networks for the acquisition of local acceleration measurements across a medium length, multi-span highway bridge is presented. The advantages, performance characteristics, and limitations of employing this emerging technology in favor of the traditional cable-based acquisition systems are discussed in the context of the in-service instrumentation and ambient vibration testing of a multi-span bridge. Of particular highlight in this study is the deployment of a large number of stationary rather than reference-based accelerometers to uniquely permit simultaneous acquisition of vibration measurements across the structure and thereby ensure consistent temperature, ambient vibration, and traffic loading. The deployment consisted of 30 dual-axis accelerometers installed across the girders of the bridge and interfaced with 30 wireless acquisition and transceiver nodes operating in two star topology networks. Real-time wireless acquisition at a per channel sampling rate of 128 samples per second was maintained across both networks for the specified test durations of 3 min with insignificant data loss. Output-only system identification of the structure from the experimental data is presented to provide estimates of natural frequencies, damping ratios, and operational mode shapes for 19 modes. The analysis of the structure under test provides a unique case study documenting the measured response of a multiple-span skewed bridge supported by elastomeric bearings. The feasibility of embedded wireless instrumentation for structural health monitoring of large civil constructions is concluded while highlighting relevant technological shortcomings and areas of further development required. In particular, previously undocumented obstacles relating to radio transmission of the sensor data using low-power 2.4 GHz wireless instrumentation, such as the effect of solid piers within the line-of-sight and the reflection of the radio waves on the surface of the water, are discussed.

The clear and detailed images of geological structures that can be obtained by seismic methods are one of the main drivers of their popularity in geological research. The quality of final geophysical images and models relies strongly on the amount of data that goes into them. Analysing several complementary seismic datasets allow an improved interpretation. Responding to this challenge, this article proposed an optimal combination of geophysical methods for near-surface applications. Multi-channel analysis of surface waves, first-arrival travel-time tomography, and ground-penetrating radar were the key supports for standard reflection seismic imaging. Ease of use and fast and cheap acquisition are some of the advantages of the mentioned methods. Considering that all recorded wave fields required minimal additional processing while offering a significant improvement in the final stack, it was worth the extra effort. Thanks to that, the better-estimated velocity filed allowed high quality images to be obtained up to 200 m. The Mesozoic bedrock was a distinct and very strong reflector in the resulting reflection seismic imaging. There was also a clearly visible depression of the horizon corresponding to erosion or a structure (syncline). Deeper, it was possible to track two or even four detachments of faulting origin.

Radial pulse signals are produced by the periodic ejection of blood from the heart, and physiological and pathological information of the human body can be analyzed by extracting the time-domain characteristics of pulse waves. However, since pulse signals are weak physiological signals on the body surface and complex, the acquisition of pulse characteristics using the traditional curvature method will produce a large error, which cannot meet the needs of pulse wave analysis in current clinical practice. To solve this problem, a multi-morphological pulse signal feature recognition algorithm based on the one-dimensional deep convolutional neural network (1D-DCNN) model is proposed. We used the multi-channel pulse diagnosis instrument independently developed by the team to collect radial pulse signals under continuous pressure of the test subjects and collected 115 subjects and extracted a total of 1300 single-cycle pulse signals and then divided these pulse signals into 6 different forms. Five types of pulse signal time-domain feature points were labeled, and five independent feature point datasets were labeled and formed five customized neural network models that were generated to train and identify the pulse feature point datasets independently. The results show that the correction coefficient () of the multi-class pulse signal processing algorithm proposed in this paper for each type of feature point recognition reaches more than 0.92. The performance is significantly better than that of the traditional curvature method, which shows the accuracy and superiority of the proposed method. Therefore, the multi-class pulse signal characteristic parameter recognition model based on the 1D-DCNN model proposed in this paper can efficiently and accurately identify pulse time-domain characteristic parameters, which can be applied to discriminate time-domain pulse information in clinical practice and assist doctors in diagnosis.

Abstract The importance of a detailed knowledge of the shear-wave velocity structure in the very shallow depth was recently stressed in strong ground motion studies. In this article, we investigate the 1D velocity and attenuation structure of the very shallow coverage of a sediment-filled valley by using surface waves from a small explosive source, recorded along a 65-m-long linear array. The group and phase velocity dispersion curves are obtained from the analysis of the multi-channel recordings and inverted for the velocity structure. The velocity model obtained in this way is then used as a new starting model for a waveform inversion process, in which both compressional- and shear-wave velocities are iteratively adjusted, obtaining a significative improvement of the fit between data and synthetics. The Q structure is investigated by using the technique described in Malagnini et al. (1995). The velocity is kept fixed, and the reference frequency for the computation of causal Q is put at 10 Hz, due to the high-frequency content of the recorded waveforms. The resulting Q values in the upper layer (QP = QS = 9 in the first 20 m in depth) are higher than those previously observed at 1 Hz in the same site (QP = QS = 2 in the first 22 m in depth), suggesting, at least in the investigated case, a frequency-dependent attenuation structure for soft-soil coverages.

Preliminary results from seismic data collected at two sites on the Teton fault reveal shallow sub-surface fault structure and a basis for evaluating the post-glacial faulting record in greater detail. These new data include high-resolution shallow 2D seismic refraction and Interferometric Multi-Channel Analysis of Surface Waves (IMASW) (O’Connell and Turner 2010) depth-averaged shear wave velocity (Vs). The Teton fault, a down-to-the east normal fault, is expressed as a distinct topographic escarpment along the base of the eastern front of the Teton Range in Wyoming. The average fault scarp height cut into deglacial surfaces in several similar valleys and an assumed 14,000 yr BP deglaciation indicates an average postglacial offset rate of 0.82 m/ka (Thackray and Staley, in review). Because the fault is located almost entirely within Grand Teton National Park (GTNP), and in terrain that is remote and difficult to access, very few subsurface studies have been used to evaluate the fault. As a result, many uncertainties exist in the present characterization of along-strike slip rate, down-dip geometry, and rupture history, among other parameters. Additionally, questions remain about the fault dip at depth. Shallow seismic data were collected at two locations on the Teton fault scarp to (1) use a non-destructive, highly portable and cost-effective data collection system to image and characterize the Teton fault, (2) use the data to estimate vertical offsets of faulted bedrock and sediment, and (3) estimate fault dip in the shallow subsurface. Vs data were also collected at three GTNP facility structures to provide measured 30 m depth-averaged Vs (Vs30) for each site. Seismic data were collected using highly portable equipment packed into each site on foot. The system utilizes a sensor line 92 m long that includes 24 geophones (channels) at 4 m intervals. At both the Taggart Lake and String Lake sites, P-wave refraction data were collected spanning the fault scarp and perpendicular to local fault strike, as well as IMASW Vs seismic lines positioned on the hanging wall to provide Vs vs. Depth profiles crossing and perpendicular to the refraction survey lines. The Taggart Lake and String Lake 2D P-wave refraction profile and IMASW Vs plots reveal buried velocity structure that is vertically offset by the Teton fault. At Taggart Lake, we interpret the velocity horizon to be the top of dense glacial sediment (possibly compacted till), which is overlain by younger, slower, sediments. This surface is offset ~13 m (down-to-the-east) across the Teton fault. The vertical offset is in agreement with the measured height of the corresponding topographic scarp (~12 - 15 m). Geomorphic analysis of EarthScope (2008) LiDAR reveals small terraces, slope inflections and an abandoned channel on the footwall side of the scarp. At String Lake, the shallow buried velocity structure is inferred as unconsolidated alluvium (till, colluvium, alluvium); this relatively low velocity zone (

Climate change induced sea-level rise (SLR) is on its increase globally. Regionally the lowlands of China, Vietnam, Bangladesh, and islands of the Malaysian, Indonesian and Philippine archipelagos are among the world’s most threatened regions. Sea-level rise has major impacts on the ecosystems and society. It threatens coastal populations, economic activities, and fragile ecosystems as mangroves, coastal salt-marches and wetlands. This paper provides a summary of the current state of knowledge of sea level-rise and its effects on both human and natural ecosystems. The focus is on coastal urban areas and low lying deltas in South-East Asia and Vietnam, as one of the most threatened areas in the world. About 3 mm per year reflects the growing consensus on the average SLR worldwide. The trend speeds up during recent decades. The figures are subject to local, temporal and methodological variation. In Vietnam the average values of 3.3 mm per year during the 1993-2014 period are above the worldwide average. Although a basic conceptual understanding exists that the increasing global frequency of the strongest tropical cyclones is related with the increasing temperature and SLR, this relationship is insufficiently understood. Moreover the precise, complex environmental, economic, social, and health impacts are currently unclear. SLR, storms and changing precipitation patterns increase flood risks, in particular in urban areas. Part of the current scientific debate is on how urban agglomeration can be made more resilient to flood risks. Where originally mainly technical interventions dominated this discussion, it becomes increasingly clear that proactive special planning, flood defense, flood risk mitigation, flood preparation, and flood recovery are important, but costly instruments. Next to the main focus on SLR and its effects on resilience, the paper reviews main SLR associated impacts: Floods and inundation, salinization, shoreline change, and effects on mangroves and wetlands. The hazards of SLR related floods increase fastest in urban areas. This is related with both the increasing surface major cities are expected to occupy during the decades to come and the increasing coastal population. In particular Asia and its megacities in the southern part of the continent are increasingly at risk. The discussion points to complexity, inter-disciplinarity, and the related uncertainty, as core characteristics. An integrated combination of mitigation, adaptation and resilience measures is currently considered as the most indicated way to resist SLR today and in the near future.References Aerts J.C.J.H., Hassan A., Savenije H.H.G., Khan M.F., 2000. Using GIS tools and rapid assessment techniques for determining salt intrusion: Stream a river basin management instrument. Physics and Chemistry of the Earth, Part B: Hydrology, Oceans and Atmosphere, 25, 265-273. Doi: 10.1016/S1464-1909(00)00014-9. Alongi D.M., 2002. Present state and future of the world’s mangrove forests. Environmental Conservation, 29, 331-349. Doi: 10.1017/S0376892902000231 Alongi D.M., 2015. The impact of climate change on mangrove forests. Curr. Clim. Change Rep., 1, 30-39. Doi: 10.1007/s404641-015-0002-x. Anderson F., Al-Thani N., 2016. Effect of sea level rise and groundwater withdrawal on seawater intrusion in the Gulf Coast aquifer: Implications for agriculture. Journal of Geoscience and Environment Protection, 4, 116-124. Doi: 10.4236/gep.2016.44015. Anguelovski I., Chu E., Carmin J., 2014. Variations in approaches to urban climate adaptation: Experiences and experimentation from the global South. Global Environmental Change, 27, 156-167. Doi: 10.1016/j.gloenvcha.2014.05.010. Arustienè J., Kriukaitè J., Satkunas J., Gregorauskas M., 2013. Climate change and groundwater - From modelling to some adaptation means in example of Klaipèda region, Lithuania. In: Climate change adaptation in practice. P. Schmidt-Thomé, J. Klein Eds. John Wiley and Sons Ltd., Chichester, UK., 157-169. Bamber J.L., Aspinall W.P., Cooke R.M., 2016. A commentary on “how to interpret expert judgement assessments of twenty-first century sea-level rise” by Hylke de Vries and Roderik S.W. Van de Wal. Climatic Change, 137, 321-328. Doi: 10.1007/s10584-016-1672-7. Barnes C., 2014. Coastal population vulnerability to sea level rise and tropical cyclone intensification under global warming. BSc-thesis. Department of Geography, University of Lethbridge, Alberta Canada. Be T.T., Sinh B.T., Miller F., 2007. Challenges to sustainable development in the Mekong Delta: Regional and national policy issues and research needs. The Sustainable Mekong Research Network, Bangkok, Thailand, 1-210. Bellard C., Leclerc C., Courchamp F., 2014. Impact of sea level rise on 10 insular biodiversity hotspots. Global Ecology and Biogeography, 23, 203-212. Doi: 10.1111/geb.12093. Berg H., Söderholm A.E., Sönderström A.S., Nguyen Thanh Tam, 2017. Recognizing wetland ecosystem services for sustainable rice farming in the Mekong delta, Vietnam. Sustainability Science, 12, 137-154. Doi: 10.1007/s11625-016-0409-x. Bilskie M.V., Hagen S.C., Medeiros S.C., Passeri D.L., 2014. Dynamics of sea level rise and coastal flooding on a changing landscape. Geophysical Research Letters, 41, 927-934. Doi: 10.1002/2013GL058759. Binh T.N.K.D., Vromant N., Hung N.T., Hens L., Boon E.K., 2005. Land cover changes between 1968 and 2003 in Cai Nuoc, Ca Mau penisula, Vietnam. Environment, Development and Sustainability, 7, 519-536. Doi: 10.1007/s10668-004-6001-z. Blankespoor B., Dasgupta S., Laplante B., 2014. Sea-level rise and coastal wetlands. Ambio, 43, 996- 005.Doi: 10.1007/s13280-014-0500-4. Brockway R., Bowers D., Hoguane A., Dove V., Vassele V., 2006. A note on salt intrusion in funnel shaped estuaries: Application to the Incomati estuary, Mozambique.Estuarine, Coastal and Shelf Science, 66, 1-5. Doi: 10.1016/j.ecss.2005.07.014. Cannaby H., Palmer M.D., Howard T., Bricheno L., Calvert D., Krijnen J., Wood R., Tinker J., Bunney C., Harle J., Saulter A., O’Neill C., Bellingham C., Lowe J., 2015. Projected sea level rise and changes in extreme storm surge and wave events during the 21st century in the region of Singapore. Ocean Sci. Discuss, 12, 2955-3001. Doi: 10.5194/osd-12-2955-2015. Carraro C., Favero A., Massetti E., 2012. Investment in public finance in a green, low carbon economy. Energy Economics, 34, S15-S18. Castan-Broto V., Bulkeley H., 2013. A survey ofurban climate change experiments in 100 cities. Global Environmental Change, 23, 92-102. Doi: 10.1016/j.gloenvcha.2012.07.005. Cazenave A., Le Cozannet G., 2014. Sea level rise and its coastal impacts. GeoHealth, 2, 15-34. Doi: 10.1002/2013EF000188. Chu M.L., Guzman J.A., Munoz-Carpena R., Kiker G.A., Linkov I., 2014. A simplified approach for simulating changes in beach habitat due to the combined effects of long-term sea level rise, storm erosion and nourishment. Environmental modelling and software, 52, 111-120. Doi.org/10.1016/j.envcsoft.2013.10.020. Church J.A. et al., 2013. Sea level change. In: Climate change 2013: The physical science basis. Contribution of working group I to the fifth assessment report of Intergovernmental Panel on Climate Change. Eds: Stocker T.F., Qin D., Plattner G.-K., Tignor M., Allen S.K., Boschung J., Nauels A., Xia Y., Bex V., Midgley P.M., Cambridge University Press, Cambridge, UK. Connell J., 2016. Last days of the Carteret Islands? Climate change, livelihoods and migration on coral atolls. Asia Pacific Viewpoint, 57, 3-15. Doi: 10.1111/apv.12118. Dasgupta S., Laplante B., Meisner C., Wheeler, Yan J., 2009. The impact of sea level rise on developing countries: A comparative analysis. Climatic Change, 93, 379-388. Doi: 10.1007/s 10584-008-9499-5. Delbeke J., Vis P., 2015. EU climate policy explained, 136p. Routledge, Oxon, UK. DiGeorgio M., 2015. Bargaining with disaster: Flooding, climate change, and urban growth ambitions in QuyNhon, Vietnam. Public Affairs, 88, 577-597. Doi: 10.5509/2015883577. Do Minh Duc, Yasuhara K., Nguyen Manh Hieu, 2015. Enhancement of coastal protection under the context of climate change: A case study of Hai Hau coast, Vietnam. Proceedings of the 10th Asian Regional Conference of IAEG, 1-8. Do Minh Duc, Yasuhara K., Nguyen Manh Hieu, Lan Nguyen Chau, 2017. Climate change impacts on a large-scale erosion coast of Hai Hau district, Vietnam and the adaptation. Journal of Coastal Conservation, 21, 47-62. Donner S.D., Webber S., 2014. Obstacles to climate change adaptation decisions: A case study of sea level rise; and coastal protection measures in Kiribati. Sustainability Science, 9, 331-345. Doi: 10.1007/s11625-014-0242-z. Driessen P.P.J., Hegger D.L.T., Bakker M.H.N., Van Renswick H.F.M.W., Kundzewicz Z.W., 2016. Toward more resilient flood risk governance. Ecology and Society, 21, 53-61. Doi: 10.5751/ES-08921-210453. Duangyiwa C., Yu D., Wilby R., Aobpaet A., 2015. Coastal flood risks in the Bangkok Metropolitan region, Thailand: Combined impacts on land subsidence, sea level rise and storm surge. American Geophysical Union, Fall meeting 2015, abstract#NH33C-1927. Duarte C.M., Losada I.J., Hendriks I.E., Mazarrasa I., Marba N., 2013. The role of coastal plant communities for climate change mitigation and adaptation. Nature Climate Change, 3, 961-968. Doi: 10.1038/nclimate1970. Erban L.E., Gorelick S.M., Zebker H.A., 2014. Groundwater extraction, land subsidence, and sea-level rise in the Mekong Delta, Vietnam. Environmental Research Letters, 9, 1-20. Doi: 10.1088/1748-9326/9/8/084010. FAO - Food and Agriculture Organisation, 2007.The world’s mangroves 1980-2005. FAO Forestry Paper, 153, Rome, Italy. Farbotko C., 2010. Wishful sinking: Disappearing islands, climate refugees and cosmopolitan experimentation. Asia Pacific Viewpoint, 51, 47-60. Doi: 10.1111/j.1467-8373.2010.001413.x. Goltermann D., Ujeyl G., Pasche E., 2008. Making coastal cities flood resilient in the era of climate change. Proceedings of the 4th International Symposium on flood defense: Managing flood risk, reliability and vulnerability, 148-1-148-11. Toronto, Canada. Gong W., Shen J., 2011. The response of salt intrusion to changes in river discharge and tidal mixing during the dry season in the Modaomen Estuary, China.Continental Shelf Research, 31, 769-788. Doi: 10.1016/j.csr.2011.01.011. Gosian L., 2014. Protect the world’s deltas. Nature, 516, 31-34. Graham S., Barnett J., Fincher R., Mortreux C., Hurlimann A., 2015. Towards fair outcomes in adaptation to sea-level rise. Climatic Change, 130, 411-424. Doi: 10.1007/s10584-014-1171-7. COASTRES-D-12-00175.1. Güneralp B., Güneralp I., Liu Y., 2015. Changing global patterns of urban expoàsure to flood and drought hazards. Global Environmental Change, 31, 217-225. Doi: 10.1016/j.gloenvcha.2015.01.002. Hallegatte S., Green C., Nicholls R.J., Corfee-Morlot J., 2013. Future flood losses in major coastal cities. Nature Climate Change, 3, 802-806. Doi: 10.1038/nclimate1979. Hamlington B.D., Strassburg M.W., Leben R.R., Han W., Nerem R.S., Kim K.-Y., 2014. Uncovering an anthropogenic sea-level rise signal in the Pacific Ocean. Nature Climate Change, 4, 782-785. Doi: 10.1038/nclimate2307. Hashimoto T.R., 2001. Environmental issues and recent infrastructure development in the Mekong Delta: Review, analysis and recommendations with particular reference to large-scale water control projects and the development of coastal areas. Working paper series (Working paper No. 4). Australian Mekong Resource Centre, University of Sydney, Australia, 1-70. Hibbert F.D., Rohling E.J., Dutton A., Williams F.H., Chutcharavan P.M., Zhao C., Tamisiea M.E., 2016. Coral indicators of past sea-level change: A global repository of U-series dated benchmarks. Quaternary Science Reviews, 145, 1-56. Doi: 10.1016/j.quascirev.2016.04.019. Hinkel J., Lincke D., Vafeidis A., Perrette M., Nicholls R.J., Tol R.S.J., Mazeion B., Fettweis X., Ionescu C., Levermann A., 2014. Coastal flood damage and adaptation costs under 21st century sea-level rise. Proceedings of the National Academy of Sciences, 111, 3292-3297. Doi: 10.1073/pnas.1222469111. Hinkel J., Nicholls R.J., Tol R.S.J., Wang Z.B., Hamilton J.M., Boot G., Vafeidis A.T., McFadden L., Ganapolski A., Klei R.J.Y., 2013. A global analysis of erosion of sandy beaches and sea level rise: An application of DIVA. Global and Planetary Change, 111, 150-158. Doi: 10.1016/j.gloplacha.2013.09.002. Huong H.T.L., Pathirana A., 2013. Urbanization and climate change impacts on future urban flooding in Can Tho city, Vietnam. Hydrol. Earth Syst. Sci., 17, 379-394. Doi: 10.5194/hess-17-379-2013. Hurlimann A., Barnett J., Fincher R., Osbaldiston N., Montreux C., Graham S., 2014. Urban planning and sustainable adaptation to sea-level rise. Landscape and Urban Planning, 126, 84-93. Doi: 10.1016/j.landurbplan.2013.12.013. IMHEN-Vietnam Institute of Meteorology, Hydrology and Environment, 2011. Climate change vulnerability and risk assessment study for Ca Mau and KienGiang provinces, Vietnam. Hanoi, Vietnam Institute of Meteorology, Hydrology and Environment (IMHEN), 250p. IMHEN-Vietnam Institute of Meteorology, Hydrology and Environment, Ca Mau PPC, 2011. Climate change impact and adaptation study in The Mekong Delta - Part A: Ca Mau Atlas. Hanoi, Vietnam: Institute of Meteorology, Hydrology and Environment (IMHEN), 48p. IPCC-Intergovernmental Panel on Climate Change, 2014. Fifth assessment report. Cambridge University Press, Cambridge, UK. Jevrejeva S., Jackson L.P., Riva R.E.M., Grinsted A., Moore J.C., 2016. Coastal sea level rise with warming above 2°C. Proceedings of the National Academy of Sciences, 113, 13342-13347. Doi: 10.1073/pnas.1605312113. Junk W.J., AN S., Finlayson C.M., Gopal B., Kvet J., Mitchell S.A., Mitsch W.J., Robarts R.D., 2013. Current state of knowledge regarding the world’s wetlands and their future under global climate change: A synthesis. Aquatic Science, 75, 151-167. Doi: 10.1007/s00027-012-0278-z. Jordan A., Rayner T., Schroeder H., Adger N., Anderson K., Bows A., Le Quéré C., Joshi M., Mander S., Vaughan N., Whitmarsh L., 2013. Going beyond two degrees? The risks and opportunities of alternative options. Climate Policy, 13, 751-769. Doi: 10.1080/14693062.2013.835705. Kelly P.M., Adger W.N., 2000. Theory and practice in assessing vulnerability to climate change and facilitating adaptation. Climatic Change, 47, 325-352. Doi: 10.1023/A:1005627828199. Kirwan M.L., Megonigal J.P., 2013. Tidal wetland stability in the face of human impacts and sea-level rice. Nature, 504, 53-60. Doi: 10.1038/nature12856. Koerth J., Vafeidis A.T., Hinkel J., Sterr H., 2013. What motivates coastal households to adapt pro actively to sea-level rise and increased flood risk? Regional Environmental Change, 13, 879-909. Doi: 10.1007/s10113-12-399-x. Kontgis K., Schneider A., Fox J;,Saksena S., Spencer J.H., Castrence M., 2014. Monitoring peri urbanization in the greater Ho Chi Minh City metropolitan area. Applied Geography, 53, 377-388. Doi: 10.1016/j.apgeogr.2014.06.029. Kopp R.E., Horton R.M., Little C.M., Mitrovica J.X., Oppenheimer M., Rasmussen D.J., Strauss B.H., Tebaldi C., 2014. Probabilistic 21st and 22nd century sea-level projections at a global network of tide-gauge sites. Earth’s Future, 2, 383-406. Doi: 10.1002/2014EF000239. Kuenzer C., Bluemel A., Gebhardt S., Quoc T., Dech S., 2011. Remote sensing of mangrove ecosystems: A review.Remote Sensing, 3, 878-928. Doi: 10.3390/rs3050878. Lacerda G.B.M., Silva C., Pimenteira C.A.P., Kopp Jr. R.V., Grumback R., Rosa L.P., de Freitas M.A.V., 2013. Guidelines for the strategic management of flood risks in industrial plant oil in the Brazilian coast: Adaptive measures to the impacts of sea level rise. Mitigation and Adaptation Strategies for Global Change, 19, 104-1062. Doi: 10.1007/s11027-013-09459-x. Lam Dao Nguyen, Pham Van Bach, Nguyen Thanh Minh, Pham Thi Mai Thy, Hoang Phi Hung, 2011. Change detection of land use and river bank in Mekong Delta, Vietnam using time series remotely sensed data. Journal of Resources and Ecology, 2, 370-374. Doi: 10.3969/j.issn.1674-764x.2011.04.011. Lang N.T., Ky B.X., Kobayashi H., Buu B.C., 2004. Development of salt tolerant varieties in the Mekong delta. JIRCAS Project, Can Tho University, Can Tho, Vietnam, 152. Le Cozannet G., Rohmer J., Cazenave A., Idier D., Van de Wal R., de Winter R., Pedreros R., Balouin Y., Vinchon C., Oliveros C., 2015. Evaluating uncertainties of future marine flooding occurrence as sea-level rises. Environmental Modelling and Software, 73, 44-56. Doi: 10.1016/j.envsoft.2015.07.021. Le Cozannet G., Manceau J.-C., Rohmer J., 2017. Bounding probabilistic sea-level projections with the framework of the possible theory. Environmental Letters Research, 12, 12-14. Doi.org/10.1088/1748-9326/aa5528.Chikamoto Y., 2014. Recent Walker circulation strengthening and Pacific cooling amplified by Atlantic warming. Nature Climate Change, 4, 888-892. Doi: 10.1038/nclimate2330. Lovelock C.E., Cahoon D.R., Friess D.A., Gutenspergen G.R., Krauss K.W., Reef R., Rogers K., Saunders M.L., Sidik F., Swales A., Saintilan N., Le Xuan Tuyen, Tran Triet, 2015. The vulnerability of Indo-Pacific mangrove forests to sea-level rise. Nature, 526, 559-563. Doi: 10.1038/nature15538. MA Millennium Ecosystem Assessment, 2005. Ecosystems and human well-being: Current state and trends. Island Press, Washington DC, 266p. Masterson J.P., Fienen M.N., Thieler E.R., Gesch D.B., Gutierrez B.T., Plant N.G., 2014. Effects of sea level rise on barrier island groundwater system dynamics - ecohydrological implications. Ecohydrology, 7, 1064-1071. Doi: 10.1002/eco.1442. McGanahan G., Balk D., Anderson B., 2007. The rising tide: Assessing the risks of climate changes and human settlements in low elevation coastal zones.Environment and urbanization, 19, 17-37. Doi: 10.1177/095624780707960. McIvor A., Möller I., Spencer T., Spalding M., 2012. Reduction of wind and swell waves by mangroves. The Nature Conservancy and Wetlands International, 1-27. Merryn T., Pidgeon N., Whitmarsh L., Ballenger R., 2016. Expert judgements of sea-level rise at the local scale. Journal of Risk Research, 19, 664-685. Doi.org/10.1080/13669877.2015.1043568. Monioudi I.N., Velegrakis A.F., Chatzipavlis A.E., Rigos A., Karambas T., Vousdoukas M.I., Hasiotis T., Koukourouvli N., Peduzzi P., Manoutsoglou E., Poulos S.E., Collins M.B., 2017. Assessment of island beach erosion due to sea level rise: The case of the Aegean archipelago (Eastern Mediterranean). Nat. Hazards Earth Syst. Sci., 17, 449-466. Doi: 10.5194/nhess-17-449-2017. MONRE - Ministry of Natural Resources and Environment, 2016. Scenarios of climate change and sea level rise for Vietnam. Publishing House of Environmental Resources and Maps Vietnam, Hanoi, 188p. Montz B.E., Tobin G.A., Hagelman III R.R., 2017. Natural hazards. Explanation and integration. The Guilford Press, NY, 445p. Morgan L.K., Werner A.D., 2014. Water intrusion vulnerability for freshwater lenses near islands. Journal of Hydrology, 508, 322-327. Doi: 10.1016/j.jhydrol.2013.11.002. Muis S., Güneralp B., Jongman B., Aerts J.C.H.J., Ward P.J., 2015. Science of the Total Environment, 538, 445-457. Doi: 10.1016/j.scitotenv.2015.08.068. Murray N.J., Clemens R.S., Phinn S.R., Possingham H.P., Fuller R.A., 2014. Tracking the rapid loss of tidal wetlands in the Yellow Sea. Frontiers in Ecology and Environment, 12, 267-272. Doi: 10.1890/130260. Neumann B., Vafeidis A.T., Zimmermann J., Nicholls R.J., 2015a. Future coastal population growth and exposure to sea-level rise and coastal flooding. A global assessment. Plos One, 10, 1-22. Doi: 10.1371/journal.pone.0118571. Nguyen A. Duoc, Savenije H. H., 2006. Salt intrusion in multi-channel estuaries: a case study in the Mekong Delta, Vietnam. Hydrology and Earth System Sciences Discussions, European Geosciences Union, 10, 743-754. Doi: 10.5194/hess-10-743-2006. Nguyen An Thinh, Nguyen Ngoc Thanh, Luong Thi Tuyen, Luc Hens, 2017. Tourism and beach erosion: Valuing the damage of beach erosion for tourism in the Hoi An, World Heritage site. Journal of Environment, Development and Sustainability. Nguyen An Thinh, Luc Hens (Eds.), 2018. Human ecology of climate change associated disasters in Vietnam: Risks for nature and humans in lowland and upland areas. Springer Verlag, Berlin.Nguyen An Thinh, Vu Anh Dung, Vu Van Phai, Nguyen Ngoc Thanh, Pham Minh Tam, Nguyen Thi Thuy Hang, Le Trinh Hai, Nguyen Viet Thanh, Hoang Khac Lich, Vu Duc Thanh, Nguyen Song Tung, Luong Thi Tuyen, Trinh Phuong Ngoc, Luc Hens, 2017. Human ecological effects of tropical storms in the coastal area of Ky Anh (Ha Tinh, Vietnam). Environ Dev Sustain, 19, 745-767. Doi: 10.1007/s/10668-016-9761-3. Nguyen Van Hoang, 2017. Potential for desalinization of brackish groundwater aquifer under a background of rising sea level via salt-intrusion prevention river gates in the coastal area of the Red River delta, Vietnam. Environment, Development and Sustainability. Nguyen Tho, Vromant N., Nguyen Thanh Hung, Hens L., 2008. Soil salinity and sodicity in a shrimp farming coastal area of the Mekong Delta, Vietnam. Environmental Geology, 54, 1739-1746. Doi: 10.1007/s00254-007-0951-z. Nguyen Thang T.X., Woodroffe C.D., 2016. Assessing relative vulnerability to sea-level rise in the western part of the Mekong River delta. Sustainability Science, 11, 645-659. Doi: 10.1007/s11625-015-0336-2. Nicholls N.N., Hoozemans F.M.J., Marchand M., Analyzing flood risk and wetland losses due to the global sea-level rise: Regional and global analyses.Global Environmental Change, 9, S69-S87. Doi: 10.1016/s0959-3780(99)00019-9. Phan Minh Thu, 2006. Application of remote sensing and GIS tools for recognizing changes of mangrove forests in Ca Mau province. In Proceedings of the International Symposium on Geoinformatics for Spatial Infrastructure Development in Earth and Allied Sciences, Ho Chi Minh City, Vietnam, 9-11 November, 1-17. Reise K., 2017. Facing the third dimension in coastal flatlands.Global sea level rise and the need for coastal transformations. Gaia, 26, 89-93. Renaud F.G., Le Thi Thu Huong, Lindener C., Vo Thi Guong, Sebesvari Z., 2015. Resilience and shifts in agro-ecosystems facing increasing sea-level rise and salinity intrusion in Ben Tre province, Mekong Delta. Climatic Change, 133, 69-84. Doi: 10.1007/s10584-014-1113-4. Serra P., Pons X., Sauri D., 2008. Land cover and land use in a Mediterranean landscape. Applied Geography, 28, 189-209. Shearman P., Bryan J., Walsh J.P., 2013.Trends in deltaic change over three decades in the Asia-Pacific Region. Journal of Coastal Research, 29, 1169-1183. Doi: 10.2112/JCOASTRES-D-12-00120.1. SIWRR-Southern Institute of Water Resources Research, 2016. Annual Report. Ministry of Agriculture and Rural Development, Ho Chi Minh City, 1-19. Slangen A.B.A., Katsman C.A., Van de Wal R.S.W., Vermeersen L.L.A., Riva R.E.M., 2012. Towards regional projections of twenty-first century sea-level change based on IPCC RES scenarios. Climate Dynamics, 38, 1191-1209. Doi: 10.1007/s00382-011-1057-6. Spencer T., Schuerch M., Nicholls R.J., Hinkel J., Lincke D., Vafeidis A.T., Reef R., McFadden L., Brown S., 2016. Global coastal wetland change under sea-level rise and related stresses: The DIVA wetland change model. Global and Planetary Change, 139, 15-30. Doi:10.1016/j.gloplacha.2015.12.018. Stammer D., Cazenave A., Ponte R.M., Tamisiea M.E., 2013. Causes of contemporary regional sea level changes. Annual Review of Marine Science, 5, 21-46. Doi: 10.1146/annurev-marine-121211-172406. Tett P., Mee L., 2015. Scenarios explored with Delphi. In: Coastal zones ecosystems services. Eds., Springer, Berlin, Germany, 127-144. Tran Hong Hanh, 2017. Land use dynamics, its drivers and consequences in the Ca Mau province, Mekong delta, Vietnam. PhD dissertation, 191p. VUBPRESS Brussels University Press, ISBN 9789057186226, Brussels, Belgium. Tran Thuc, Nguyen Van Thang, Huynh Thi Lan Huong, Mai Van Khiem, Nguyen Xuan Hien, Doan Ha Phong, 2016. Climate change and sea level rise scenarios for Vietnam. Ministry of Natural resources and Environment. Hanoi, Vietnam. Tran Hong Hanh, Tran Thuc, Kervyn M., 2015. Dynamics of land cover/land use changes in the Mekong Delta, 1973-2011: A remote sensing analysis of the Tran Van Thoi District, Ca Mau province, Vietnam. Remote Sensing, 7, 2899-2925. Doi: 10.1007/s00254-007-0951-z Van Lavieren H., Spalding M., Alongi D., Kainuma M., Clüsener-Godt M., Adeel Z., 2012. Securing the future of Mangroves. The United Nations University, Okinawa, Japan, 53, 1-56. Water Resources Directorate. Ministry of Agriculture and Rural Development, 2016. Available online: http://www.tongcucthuyloi.gov.vn/Tin-tuc-Su-kien/Tin-tuc-su-kien-tong-hop/catid/12/item/2670/xam-nhap-man-vung-dong-bang-song-cuu-long--2015---2016---han-han-o-mien-trung--tay-nguyen-va-giai-phap-khac-phuc. Last accessed on: 30/9/2016. Webster P.J., Holland G.J., Curry J.A., Chang H.-R., 2005. Changes in tropical cyclone number, duration, and intensity in a warming environment. Science, 309, 1844-1846. Doi: 10.1126/science.1116448. Were K.O., Dick O.B., Singh B.R., 2013. Remotely sensing the spatial and temporal land cover changes in Eastern Mau forest reserve and Lake Nakuru drainage Basin, Kenya. Applied Geography, 41, 75-86. Williams G.A., Helmuth B., Russel B.D., Dong W.-Y., Thiyagarajan V., Seuront L., 2016. Meeting the climate change challenge: Pressing issues in southern China an SE Asian coastal ecosystems. Regional Studies in Marine Science, 8, 373-381. Doi: 10.1016/j.rsma.2016.07.002. Woodroffe C.D., Rogers K., McKee K.L., Lovdelock C.E., Mendelssohn I.A., Saintilan N., 2016. Mangrove sedimentation and response to relative sea-level rise. Annual Review of Marine Science, 8, 243-266. Doi: 10.1146/annurev-marine-122414-034025.

In present research, Vs30 and dynamic properties of soil for ten identified sites in the campus of the Rajiv Gandhi Technological University located in Bhopal (India) are evaluated using MASW method. Shear wave velocity (Vs) profile using three steps procedure consisting of obtaining multichannel data record on field, dispersion curve analysis and inversion is generated. The properties of soil such as density, shear modulus and poison’s ratio are calculated using MASW. The poisson’s ratio, soil density and the shear modulus are observed to vary in the ranges of 0.41 to 0.27, 1.80 to 2.11 g/cc and 46 to 409 MPa respectively along depth of soil. The shear wave velocity across depth is varying between 160 to 407 m/s indicating change in soil type from mostly soft clay soil, stiff soil to a very dense soil and soft rock.

AbstractLandslides following the development of slope instability can have serious consequences. Geophysical surveys have potential to aid in the understanding of landslides and their instability. This study described a landslide that occurred under particular geomorphological and meteorological conditions in Erenler (Sakarya, NW Türkiye) using electrical resistivity tomography (ERT) and multi‐channel analysis of surface waves (MASW) surveys and mechanical drillings. Data showed that the landslide is characterized by downslope movement of an altered clay unit over a claystone unit. The traditional landslide model used to interpret geoelectric data involves sliding of a relatively low‐resistivity material over higher resistivity bedrock. Here, the ERT survey showed a relatively high‐resistivity sliding material moving over relatively low‐resistivity bedrock units corresponding to the claystone unit. The relatively lower resistivity of the whole study area was related to the clay‐rich materials detected in the boreholes. This low‐resistivity unit was detected at high velocity in the MASW section, and it was understood that this layer was a compact structure acting like bedrock. The detected slip surfaces, landslide scars and slip surface toe indicate that the movement character of the landslide is retrogressive. The study results showed that the integrated and comparative use of different geophysical methods effectively reduces interpretation uncertainties and potential errors and leads to much better landslide characterization.

Liquefaction occurs in shallow, loose, saturated deposits of cohesionless soils subjected to strong shearing stresses. This leads to the transfer of stress from the soil skeleton to the pore water precipitating a decrease in effective stress and shear resistance of the soil. The study gives the results of the liquefaction potential assessment in some part of Lagos wetland areas of Lagos. The aim of this study was to assess the liquefaction potential through the evaluation of its severity in response to Earth tremors. In order to achieve this purpose, Multi-channel Analysis of Surface waves (MASW) and Cone penetration testing (CPT) were carried out. For an optimal coverage of the study area, twenty-four channels 4.5Hz geophones connected to the ABEM Mark 6 Seismograph through two cable reels were used to detect the generated seismic wave produced by the weight drop of about 19.1 kg. The CPT soundings for assessing subsurface stratigraphy with respect to liquefiable soils were carried out with a 10-Ton Dutch Cone Penetrometer. The softwares used were SeisImager, for processing the MASW data and CLiq for the CPT measurements. The shear wave velocity models were generated for the MASW measurements. The models show that sand sediments with velocity ranging from 118 - 279 m/s dominated most of the study area. Also, the results show that for the potential liquefiable sands identified, the shear wave velocity ranges between 118.0 – 180 m/s delineated at depths between 10.0 – 20.0 m within study profile an is typical of liquefiable sands. Simplified procedure of assessment of Liquefaction potential from CPT showed a model curve whereby some CPT points were within the liquefiable zones.

Geophysical surveys provide an efficient and non-invasive means of studying subsurface conditions in numerous sedimentary settings. In this study, we explore the application of three geophysical methods to a proglacial environment, namely ground penetrating radar (GPR), seismic refraction and multi-channel analysis of surface waves (MASW). We apply these geophysical methods to three glacial landforms with contrasting morphologies and sedimentary characteristics, and we use the various responses to assess the applicability and limitations of each method for these proglacial targets. Our analysis shows that GPR and seismic (refraction and MASW) techniques can provide spatially extensive information on the internal architecture and composition of moraines, but careful survey designs are required to optimise data quality in these geologically complex environments. Based on our findings, we define a number of recommendations and a potential workflow to guide future geophysical investigations in analogous settings. We recommend the initial use of GPR in future studies of proglacial environments to inform (a) seismic survey design and (b) the selection of seismic interpretation techniques. We show the benefits of using multiple GPR antenna frequencies (e.g., 25 and 100 MHz) to provide decimetre scale imaging in the near surface (e.g., < 15 m) while also enabling signal penetration to targets at up to ∼40 m depth (e.g., bedrock). This strategy helps to circumvent changes in radar signal penetration resulting from variations in substrate conductivity or abundant scatterers. Our study also demonstrates the importance of combining multiple geophysical methods together with ground-truthing through sedimentological observations to reduce ambiguity in interpretations. Implementing our recommendations will improve geophysical survey practice in the field of glacial geology and allow geophysical methods to play an increasing role in the interpretation of glacial landforms and sediments.