Fault (geology)

About: Fault (geology) is a research topic. Over the lifetime, 26732 publications have been published within this topic receiving 744535 citations.

Late Cenozoic right‐lateral strike‐slip faulting in southern Tibet

Abstract: Field observations collected during the Sino-French Himalaya-Tibet cooperation project (1980–1982) show that right-lateral faulting between southern and northern Tibet, roughly along the “chord” joining the eastern and western syntaxes of the Himalayan arc, is a major component of the active tectonics north of the Himalayas Just north of the well developed rifts of southern Tibet, we studied three right-lateral, 100–200 km long, strike-slip faults forming an en echelon array along that chord Evidence for earthquake surface breaks was found on each of these faults For the M = 8, Beng Co (or Damxung) strike-slip earthquake of November 18, 1951, rupture parameters could be constrained to be ū = 8 ± 2 m and L = 90 km Offset glacial and postglacial morphological markers (105 years and 104 years BP) imply displacement rates of the order of 1–2 cm/yr on the three faults The en echelon fault zone appears to extend westward ≈2000 km across the plateau to the Karakorum fault and is thus referred to as the Karakorum-Jiali fault zone (KJFZ) Fast rates of slip on it and on faults along the northern rim of Tibet appear to contrast with the slower rates of deformations in the interior of the plateau Our estimates of slip rates on the strike-slip and normal faults of southeastern Tibet suggest that eastward extrusion of North Tibet between the right-lateral KJFZ and the left-lateral Altyn Tagh and Kun Lun faults absorbs at least 30% of the present convergence between India and Asia We propose an instantaneous velocity model of the active tectonics of Asia compatible with such faulting rates and geometries Evidence for Tertiary right-lateral strike-slip movements in southern Tibet and around the eastern syntaxis of the Himalayas is also found in the structural record Offsets of various large-scale geological features imply that these movements have been large

Pericollisional Strike Slip Faults and Synorogenic Basins, Canadian Cordillera

Abstract: During large scale convergence of oceanic and arc type lithospheric fragments towards a cratonic promontory along western North America from Middle Jurassic through Paleogene time non subductable crust of the approaching Pacific realm was deflected dextrally northward or sinistrally southward from this reverse indenter in the California Nevada region Paleontologic and paleomag netic data suggest oblique dextral displacements on the order of 1 500 to 2 000 km for the accreted terranes in the western Cordillera of Canada These dextral displacements were first concentrated along closing sutures from Middle Jurassic to Early Cretaceous time later they were also taken up by peri collisional fault zones which propagated into the western parts of the Cordilleran thrust belt and involved the Coast Plutonic Complex mid Cretaceous to Paleocene A subduction in the thrust belt and inferred B subduction west of the Coast Plutonic Complex were thus accompanied by dextral displacements within the Omineca and Coast fault arrays respectively imparting northwest directed stretching fabrics onto ductile metamorphic or igneous rocks and discrete fault strands on high level crustal rocks The convergent strike slip fault motions in the Canadian Cordillera created mainly sedimentary source areas rather than subsiding basins Pericollisional basins that did receive clastic materials from zones of oblique convergence were I marginal basins in the process of closing 2 relict or tectonically overloaded depressions on accreting terranes 3 foreland basins created by thrust prop agation in the miogeoclinal succession and 4 small pull apart or restraining bend depressions near high angle strike slip faults Basins in the accreted terrane complexes west of the Cordilleran thrust belt received most of their detrital material from exposed volcanic plutonic and oceanic sedimentary rocks the predominantly turbiditic basin fill suffered repeated deformation high sustained heat flow and intrusive activity The foreland basin to the east of the thrust belt on the other hand received most of its detrital input from carbonate and quartz rich clastic rocks of the miogeocline and metamorphosed equivalents the predominantly shallow water clastic deposits of the foreland basin experienced considerably less deformation and thennal alteration than the varied sedimentary assemblages of the accreted belt

Slip maxima at fault junctions and rupturing of barriers during the 2008 Wenchuan earthquake

Abstract: The disastrous 12 May 2008 Wenchuan earthquake in China took the local population as well as scientists by surprise Although the Longmen Shan fault zone—which includes the fault segments along which this earthquake nucleated—was well known, geologic and geodetic data indicate relatively low (<3 mm yr−1) deformation rates Here we invert Global Positioning System and Interferometric Synthetic Aperture Radar data to infer fault geometry and slip distribution associated with the earthquake Our analysis shows that the geometry of the fault changes along its length: in the southwest, the fault plane dips moderately to the northwest but becomes nearly vertical in the northeast Associated with this is a change in the motion along the fault from predominantly thrusting to strike-slip Peak slip along the fault occurs at the intersections of fault segments located near the towns of Yingxiu, Beichuan and Nanba, where fatalities and damage were concentrated We suggest that these locations represent barriers that failed in a single event, enabling the rupture to cascade through several fault segments and cause a major moment magnitude (Mw) 79 earthquake Using coseismic slip distribution and geodetic and geological slip rates, we estimate that the failure of barriers and rupture along multiple segments takes place approximately once in 4,000 years The devastating Wenchuan earthquake in 2008 struck along a fault zone that showed low rates of deformation Analysis of GPS and InSAR data suggests that, as structural barriers failed during a single earthquake, the rupture cascaded across multiple fault segments, which may explain the high magnitude of the event

Continental fault structure and the shallow earthquake source

Abstract: Plate boundaries in continental crust are generally less sharply defined than in the oceans, with seismicity spread over broad areas. Interplate displacements appear to be largely accommodated by networks of major fault zones. A simple 2-level model for these important structures accounts for the depth distribution of most continental earthquakes, and for the observed range of faulting styles and associated rock deformation textures. The model consists of a seismogenic frictional slip regime overlying quasi-plastic mylonite belts wherein shearing is largely accommodated aseismically, due mainly to the changing response of quartz to deformation with increasing temperature. Shear resistance increases with depth to a peak value in the vicinity of the frictiona1/quasi-plastic transition and then decreases rapidly. The depth to which microseismic activity extends appears inversely related to regional heat flow and can be satisfactorily modelled as the frictional/quasi-plastic transition for different geotherms using laboratory determined flow laws for quartz-bearing rocks. Larger earthquake ruptures ( M > 5.5) tend to nucleate near the base of the seismogenic regime in the region inferred to have the highest shear resistance and concentration of distortional strain energy. Consideration is also given to the depression of isotherms and seismic activity in regions of thrusting, and to the question of the downward continuation of major fault zones through the lithosphere. Decoupling of the upper crust on flat-lying shear zones may accompany higher-level dip-slip (and perhaps in some circumstances, strike-slip) faulting, being favoured by above average continental heat flow and a high quartz content in the middle or deep crust. The average level of deviatoric stress within the seismogenic regime remains an outstanding problem.