Total and incremental left-lateral displacement across the East Gobi Fault Zone, southern Mongolia: Implications for timing and modes of polyphase intracontinental deformation
19
Citation
114
Reference
10
Related Paper
Citation Trend
Salt tectonics
Cite
Citations (0)
ABSTRACT The 17 June 2018 MJMA 6.1 (Mw 5.5) Osaka earthquake exhibits a large non–double‐couple component (∼26%), and its aftershock sequence shows a complicated spatial pattern. To better understand the ruptured faults, we relocate the earthquake sequence using P and S arrival times and waveform cross correlations and calculate the focal mechanisms of all MJMA≥2.5 (Mw≥2.3) earthquakes within three months after the mainshock using P‐wave first‐motion polarities and S/P amplitude ratios. Relocated aftershocks image several faults, the northeast‐striking strike‐slip fault, the north‐northwest‐striking reverse fault, and at least two small northwest‐striking features. P‐wave first motions of the mainshock indicate nearly a pure thrust mechanism. We deduce that the earthquake sequence started from a north‐northwest‐striking reverse fault and propagated to a northeast‐striking strike‐slip fault. The aligned strike‐slip aftershocks occurring in the vicinity of the northeast‐striking strike‐slip fault delineates the growth of several newly formed or reactivated northwest‐striking Riedel shears that are conjugated to the northeast‐striking strike‐slip fault.
Thrust fault
Sequence (biology)
Focal mechanism
Cite
Citations (18)
Paleontologists long have argued that the most important evolutionary radiation of mammals occurred during the early Cenozoic, if not that all eutherians originated from a single common post-Cretaceous ancestor. Nonetheless, several recent molecular analyses claim to show that because several interordinal splits occurred during the Cretaceous, a major therian radiation was then underway. This claim conflicts with statistical evidence from the well-sampled latest Cretaceous and Cenozoic North American fossil record. Paleofaunal data confirm that there were fewer mammalian species during the latest Cretaceous than during any interval of the Cenozoic, and that a massive diversification took place during the early Paleocene, immediately after a mass extinction. Measurement data show that Cretaceous mammals were on average small and occupied a narrow range of body sizes; after the Cretaceous-Tertiary mass extinction, there was a rapid and permanent shift in the mean. The fact that there was an early Cenozoic mammalian radiation is entirely compatible with the existence of a few Cretaceous splits among modern mammal lineages.
Extinction (optical mineralogy)
Fossil Record
Evolution of mammals
Mammal
Cite
Citations (266)
A conceptual three-dimensional flower structure model of strike-slip faulting is proposed to explain the occurrence of earthquakes in the New Madrid seis- mic zone (NMSZ) and to illustrate the potential rupture faults for the 1811-1812 earth- quake sequences. The proposed NMSZ model is based on elastic dislocation theory and concepts of material failure under a stress field. Using a conceptual model of a strike-slip subsidiary fault array, we identify tectonic features (geological structures) that are oriented properly relative to regional stresses and classify the regions where stresses might be expected to be amplified. The brittle upper crust in the vicinity of the NMSZ is modeled as a uniform over- burden with a horizontal-basal surface, which rests on a horizontal ductile lower crust that is cut by a vertical, northeast-striking right-lateral strike-slip shear zone. We acknowledge that many favorably oriented preexisting faults have been exploited as components of the flower structure. The brittle overburden material is subject to sim- ple shearing stress parallel to the deep-seated lower crustal shear zone, and preexisting faults of the Reelfoot rift system give the upper crust a mechanical anisotropy (planes of weakness striking northeast) that is the correct orientation for development of P shear faults. The deep-seated fault movement deforms the overlying upper crust that controls the structural geometry, the modern seismicity, and the large earthquake sequences in the NMSZ. The three-dimensional NMSZ model offaulting developed in this study shows that the Bootheel and Big Creek lineaments, inferred to be two subparallel P shear faults rooted in a deep-seated fault in the lower crust, are significant in shaping the geometry of the NMSZ. These series of faults produce a large-scale flower structure in cross section. The proposed NMSZ model uses the intersections of the deep-seated fault and the two subparallel P shear faults for the locations of the 1811 and 1812 earth- quakes. The model gives rise to a predictable pattern of surface deformation that is in good agreement with the observed seismicity patterns in the region.
Seismic zone
Cite
Citations (19)
Abstract Northern Thailand is located in a structurally complex area between three major tectonic regimes, a region of extensional tectonics to the south and two major strike-slip zones, the Sagaing fault zone to the west and the Red River fault zone to the northeast. Cenozoic tectonics in northern Thailand resulted from the collision between the Indian plate and Eurasia. The continued indentation of the Indian plate into Eurasia caused polyphase extrusion of Sundaland and the movement of major strike-slip faults. The movement of these faults accompanying the regional east-west extension during Late Oligocene to Early Miocene initiated the formation of the Tertiary basins. Thirty-six major faults and forty-two intra-cratonic depositional basins in northern Thailand have been recognized and delineated using Landsat TM images. More than 70% of these basins are related to strike-slip tectonics. Five basin types have been recognized on the basis of geometric and kinematic considerations. These are fault-tip basins, pull-apart basins, fault-wedge basins, fault zone basins, and extensional basins. The opening and development of these basins was influenced by the movement of NW-trending dextral faults and NE-trending sinistral faults associated with north-south shortening and east-west extension.
Cite
Citations (20)
Summary Authors investigated main aspects of tectonics impact on sedimentation process of Western Siberian Upper Cretaceous deposits. Four seismic sequences were delaminated in Upper Cretaceous deposits in which several benches were determined. Periodic regression episodes in Upper Cretaceous depositions were detected. Tectonic faults influence on stratigraphic units geological structure was defined.
Sedimentation
Cite
Citations (0)
In the French western Alps, east of Grenoble, we identify the Belledonne Border Fault as an active seismic fault. This identification is based on the seismic monitoring of the Grenoble area by the Sismalp seismic network over the past 12 yr (1989–2000). We located a set of earthquakes with magnitudes ranging from 0 to 3.5 along a ∼50 km long alignment which runs in a N30°E direction on the western flank of the Belledonne crystalline massif. Available focal solutions for these events are consistent with this direction (N36°E strike-slip fault with right-lateral displacement). These events along the Belledonne Border Fault have a mean focal depth of ∼7 km (in the crystalline basement), with a probably very low slip rate. The Belledonne Border Fault has never been mapped at the surface, where the otherwise heavily folded and faulted Mesozoic cover makes this identification difficult. Historical seismicity also shows that, over the past two and a half centuries, a few events located mainly along the southern part of the Belledonne Border Fault caused damage, with the magnitude 4.9 1963 Monteynard earthquake reaching intensity VII. The most recent damaging event in the study area is the magnitude 3.5 1999 Laffrey earthquake (intensity V–VI). Although its epicentre lies at the southern tip of the Belledonne Border Fault, there is clear evidence that aftershocks were activated by the left-lateral slip of a N122°E-striking fault. The length of the Belledonne Border Fault, which could easily accommodate a magnitude 6 event, as well as the proximity to the Isère valley with its unlithified Quaternary deposits up to 500 m thick known to generate marked site effects, make the identification of the Belledonne Border Fault an important step in the evaluation of seismic risk in the Grenoble area. Besides, the activity observed on the fault will now have to be taken into account in future geodynamic models of the western Alps.
Epicenter
Massif
Elastic-rebound theory
Cite
Citations (96)