Academic literature on the topic 'Right-lateral faults'

Abstract The M 6.2 Elmore Desert Ranch earthquake of 24 November 1987 was associated spatially and probably temporally with left-lateral surface rupture on many northeast-trending faults in and near the Superstition Hills in western Imperial Valley. Three curving discontinuous principal zones of rupture among these breaks extended northeastward from near the Superstition Hills fault zone as far as 9 km; the maximum observed surface slip, 12.5 cm, was on the northern of the three, the Elmore Ranch fault, at a point near the epicenter. Twelve hours after the Elmore Ranch earthquake, the M 6.6 Superstition Hills earthquake occurred near the northwest end of the right-lateral Superstition Hills fault zone. Surface rupture associated with the second event occurred along three strands of the zone, here named North and South strands of the Superstition Hills fault and the Wienert fault, for 27 km southeastward from the epicenter. In contrast to the left-lateral faulting, which remained unchanged throughout the period of investigation, the right-lateral movement on the Superstition hills fault zone continued to increase with time, a behavior that was similar to other recent historical surface ruptures on northwest-trending faults in the Imperial Valley region. We measured displacements over 339 days at as many as 296 sites along the Superstition Hills fault zone, and repeated measurements at 49 sites provided sufficient data to fit with a simple power law. Data for each of the 49 sites were used to compute longitudinal displacement profiles for 1 day and to estimate the final displacement that measured slips will approach asymptotically several years after the earthquakes. The maximum right-lateral slip at 1 day was about 50 cm near the south-central part of the North strand of Superstition Hills fault, and the predicted maximum final displacement is probably about 112 cm at Imler Road near the center of the South strand of the Superstition Hills fault. The overall distributions of right-lateral displacement at 1 day and the estimated final slip are nearly symmetrical about the midpoint of the surface rupture. The average estimated final right-lateral slip for the Superstition Hills fault zone is about 54 cm. The average left-lateral slip for the conjugate faults trending northeastward is about 23 cm. The southernmost ruptured member of the Superstition Hills fault zone, newly named the Wienert fault, extends the known length of the zone by about 4 km. The southern half of this fault, south of New River, expressed only vertical displacement on a sinuous trace. The maximum vertical slip by the end of the observation period there was about 25 cm, but its growth had not ceased. Photolineaments southeast of the end of new surface rupture suggest continuation of the Superstition Hills fault zone in farmland toward Mexico.

AbstractThe Doruneh Fault System is one of the major transcurrent faults in central Asia, extending ~900 km from western Afghanistan into West-Central Iran. The left-lateral Doruneh Fault System is also a key structure in the Arabia–Eurasia collisional zone, bounding the northern margin of the independent Central Iranian Microplate. The Doruneh Fault System exhibits a curved geometry, and is divided here into three segments: Eastern, Central and Western. We present the results of geological, structural and geomorphic studies into the nature of recent activity along the Doruneh Fault System segments. A surprising observation is that small, relatively young drainage systems often show recent systematic left-lateral displacement across the fault, whereas large rivers indicate a former more complex right-lateral history. Furthermore, the existence of right-lateral offsets of pre-Pliocene rocks and S-C fabrics confirm this earlier phase of right-lateral movement on the fault. We suggest that the early right-lateral kinematics resulted from an earlier NW–SE-directed regional shortening, associated with the anticlockwise rotation of the Central Iranian Microplate. The shortening is characterized by the NE–SW-striking en échelon folds within the fault slivers, the right-lateral Taknar imbricate fan and the superimposed folding exposed north of Kashmar. Thus, assuming an initiation age of Eocene (55.8 Ma) for the fault, we estimate a former right-lateral slip rate of about 5.2–5.5 mm yr−1, which accompanied the 35° anticlockwise rotation of the Central Iranian Microplate. According to our study, the youngest units exhibiting right-lateral displacement are Middle Miocene in age, suggesting a post-Middle Miocene timing for the onset of slip-sense inversion.

The Suleiman Fold-Thrust Belt represents an active deformational front at the western margin of the Indian plate and has been a locus of major earthquakes. This study focuses on the western part of the Suleiman Fold-Thrust Belt that comprises two parallel NW–SE oriented faults: Harnai Fault and Karahi Fault. These faults have known thrust components; however, there remains uncertainty about the lateral component of motion. This work presents the new observation of surface deformation using the Small Baseline Subset (SBAS), Interferometric Synthetic Aperture Radar (InSAR) technique on Sentinel-1A datasets to decompose displacement into the vertical and horizontal components employing ascending and descending track geometries. The subsurface structural geometry of this area was assessed using 2D seismic and well data. In addition, geomorphic indices were calculated to assess the relative tectonic activity of the area. InSAR results show that the Karahi Fault has a ~15 mm right-lateral movement for descending and ~10 mm/for ascending path geometries. The Harnai Fault does not show any lateral movement. Seismic data are in agreement with the InSAR results suggesting that the Harnai Fault is a blind thrust. This work indicates that the block between these two faults displays a clockwise rotation that creates the “bookshelf model”.

AbstractThe Dongying anticline is an E-W striking complex fault-bounded block unit which located in the central Dongying Depression, Bohai Bay Basin. The anticline covers an area of approximately 12 km2. The overlying succession, which is mainly composed of Tertiary strata, is cut by normal faults with opposing dips. In terms of the general structure, the study area is located in a compound transfer zone with major bounding faults to the west (Ying 1 fault) and east (Ying -8 and -31 faults). Using three-dimensional seismic data, wireline log and checkshot data, the geometries and kinematics of faults in the transfer zone were studied, and fault displacements were calculated. The results show that when activity on the Ying 1 fault diminished, displacement was transferred to the Ying -8, Ying -31 and secondary faults so that total displacement increased. Dynamic analysis shows that the stress fields in the transfer zone were complex: the northern portion was a left-lateral extensional shear zone, and the southern portion was a right-lateral extensional shear zone. A model of potential hydrocarbon traps in the Dongying transfer zone was constructed based on the above data combined with the observed reservoir rock distribution and the sealing characteristics of the faults. The hydrocarbons were mainly expulsed from Minfeng Sag during deposition periods of Neogene Guantao and Minghuazhen Formations, and migrated along major faults from source kitchens to reservoirs. The secondary faults acted as barriers, resulting in the formation of fault-bound compartments. The high points of the anticline and well-sealed traps near secondary faults are potential targets. This paper provides a reservoir formation model of the low-order transfer zone and can be applied to the hydrocarbon exploration in transfer zones, especially the complex fault block oilfields in eastern China.