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Fault (geology)

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


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Journal ArticleDOI
TL;DR: The Chi-Chi earthquake was the largest on-land earthquake to occur in Taiwan in the twentieth century as mentioned in this paper, which caused severe damage in central western Taiwan: the excited strong shaking projected impact at cities as far as 150 km away and destroyed several high-rise buildings.
Abstract: The Chi-Chi earthquake was the largest onland earthquake to occur in Taiwan in the twentieth century. It inflicted severe damage in central western Taiwan: the excited strong shaking projected impact at cities as far as 150 km away and destroyed several high-rise buildings in the Taipei basin. Having a very complex source, the Chi-Chi earthquake ruptured the 100-km-long Chelungpu fault in a series of jumping dislocations that did not follow a process commonly assumed for an orderly propagating rupture. Furthermore, the rupture developed over a surface that was by no means planar. Principally a N-S-trending thrust of shallow (30°) dip to the east, the northern end of the ruptured Chelungpu fault turned into a more easterly trending rupture surface with an oblique-slip motion. The recently completed Taiwan Strong-Motion Instrumentation Program (TSMIP) with more than 600 modern digital instruments scored the historically largest and most significant strong-motion data recovery. In the meantime, the upgraded Taiwan Central Weather Bureau Seismic Network (CWBSN), all with digital telemetered stations each having six components in both high- and low-gain operations, electronically issued earthquake information (hypocenter, magnitude, and isoseismal map) within minutes of the mainshock to all pertinent emergency management agencies. This rapid reporting significantly improved timely emergency response and effective dispatching of rescue missions. Based on these local data, as well as on GPS, leveling, and geological ground truth observations of the surface rupture, preliminary results show that the rupture started at the southern part of the Chelungpu fault. Dislocations (or the rupture of asperities) jumped around behind the S -wave front in a rather random spatial distribution by which no rupture propagating velocity can be properly defined. Large ground acceleration, some over 1 g , occurred in the southern part of the Chelungpu fault where the rupture initiated. Toward the northern section of the Chelungpu fault, a decrease in ground acceleration was accompanied with an increase in ground velocity (to as much as 300 cm/sec) and ground displacement (to as much as 8 m). Most of the large motions were confined to the hanging wall (i.e., the eastern block of the thrust), and relatively small ground motions occurred in the footwall. Thus the hanging wall contributed the most to the rupture process. During the later part of the rupture, the N-S-trending Chelungpu fault made an easterly bend and the thrust motion turned into a more oblique-slip motion at the northern end. Meanwhile, the strong dynamic rupturing process triggered two M 6 events, each one having occurred in the vicinity of a known fault: one off the southern end and the other off the northern end of the Chelungpu fault. Manuscript received 12 December 2000.

253 citations

Journal ArticleDOI
01 Oct 2001-Geology
TL;DR: In this paper, a compilation of dip estimates from focal mechanisms of shallow, intracontinental, normal-slip earthquakes (M. 5.5; slip vector raking 90 86 308 in the fault plane) where the rupture plane is unambiguously discriminated is presented.
Abstract: Debate continues as to whether normal faults may be seismically active at very low dips (d , 308) in the upper continental crust. An updated compilation of dip estimates (n 5 25) has been prepared from focal mechanisms of shallow, intracontinental, normal-slip earthquakes (M . 5.5; slip vector raking 90 86 308 in the fault plane) where the rupture plane is unambiguously discriminated. The dip distribution for these moderate-to-large normal fault ruptures extends from 658 . d . 308, corresponding to a range, 258 , ur , 608, for the reactivation angle between the fault and inferred vertical s1. In a comparable data set previously obtained for reverse fault ruptures (n 5 33), the active dip distribution is 108 , d5u r , 608. For vertical and horizontal s1 trajectories within extensional and compressional tectonic regimes, respectively, dip-slip reactivation is thus restricted to faults oriented at ur # 608 to inferred s1. Apparent lockup at ur 608 in each dip distribution and a dominant 30 86 58 peak in the reverse fault dip distribution, are both consistent with a friction coefficient ms 0.6, toward the bottom of Byerlee’s experimental range, though localized fluid overpressuring may be needed for reactivation of less favorably oriented faults.

253 citations

Journal ArticleDOI
TL;DR: A map-view palinspastic restoration of tectonic units in the Alps, Carpathians and Dinarides reveals the plate-tectonic configuration before the onset of Miocene to recent deformations as mentioned in this paper.
Abstract: A map-view palinspastic restoration of tectonic units in the Alps, Carpathians and Dinarides reveals the plate tectonic configuration before the onset of Miocene to recent deformations. Estimates of shortening and extension from the entire orogenic system allow for a semi-quantitative restoration of translations and rotations of tectonic units during the last 20 Ma. Our restoration yielded the following results: (1) The Balaton Fault and its eastern extension along the northern margin of the Mid-Hungarian Fault Zone align with the Periadriatic Fault, a geometry that allows for the eastward lateral extrusion of the Alpine-Carpathian-Pannonian (ALCAPA) Mega-Unit. The Mid-Hungarian Fault Zone accommodated simultaneous strike-perpendicular shortening and strike-slip movements, concomitant with strike-parallel extension. (2) The Mid-Hungarian Fault Zone is also the locus of a former plate boundary transforming opposed subduction polarities between Alps (including Western Carpathians) and Dinarides. (3) The ALCAPA Mega-Unit was affected by 290 km extension and fits into an area W of present-day Budapest in its restored position, while the Tisza-Dacia Mega-Unit was affected by up to 180 km extension during its emplacement into the Carpathian embayment. (4) The external Dinarides experienced Neogene shortening of over 200 km in the south, contemporaneous with dextral wrench movements in the internal Dinarides and the easterly adjacent Carpatho-Balkan orogen. (5) N-S convergence between the European and Adriatic plates amounts to some 200 km at a longitude of 14° E, in line with post-20 Ma subduction of Adriatic lithosphere underneath the Eastern Alps, corroborating the discussion of results based on high-resolution teleseismic tomography.

252 citations

Journal ArticleDOI
TL;DR: The velocity field within a 100 km-broad zone centered on the San Andreas fault between the Mexican border and San Francisco Bay has been inferred from repeated surveys of trilateration networks in the 1973-1989 interval as mentioned in this paper.
Abstract: The velocity field within a 100-km-broad zone centered on the San Andreas fault between the Mexican border and San Francisco Bay has been inferred from repeated surveys of trilateration networks in the 1973–1989 interval. The velocity field has the appearance of a shear flow that remains parallel to the local strike of the fault even through such major deflections as the big bend of the San Andreas fault in the Transverse Ranges of southern California. Across-strike profiles of the fault-parallel component of velocity exhibit the expected sigmoidal shape, whereas across-strike profiles of the fault-normal component of velocity are flat and featureless. No significant convergence upon the fault is observed even along the big bend sector of the fault. Simple dislocation models can explain most of the features of the observed velocity field, but those explanations are not unique. About 35 mm/yr of relative plate motion is accounted for within the span of the trilateration networks. Geologic studies indicate that the secular slip rate on the San Andreas fault is about 35 mm/yr. The agreement between these two estimates implies that most of the strain accumulation is elastic and will be recovered in subsequent earthquakes. The relative motion observed across the San Andreas fault (35 mm/yr) plus that observed across the Eastern California shear zone (8 mm/yr) accounts for most (43 mm/yr) of the observed North America-Pacific relative plate motion (47 mm/yr).

252 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of frictional heating on the thermal, hydrologic, and mechanical response of a small patch of the failure surface were investigated and a fault model was proposed to examine the parameters that control the fault response and to determine their critical range of values where thermal pressurization is significant.
Abstract: The mechanical response of a fault zone during an earthquake may be controlled by the diffusion of excess heat and fluid pressures generated by frictional heating. In this study we formulate a fault model which incorporates the effects of frictional heating on the thermal, hydrologic, and mechanical response of a small patch of the failure surface. This model is used to examine the parameters that control the fault response and to determine their critical range of values where thermal pressurization is significant. The problem has two time scales: a characteristic slip duration and a characteristic time for thermal pressurization. The slip duration is set by the fault geometry. The characteristic time for thermal pressurization is set by the slip rate, the friction coefficient, and the thermal and hydraulic characteristics of the medium. The response of the fault depends on the relative magnitude of these two times. Results suggest that the fault width and hydraulic characteristics of the fault zone and adjacent medium are the primary parameters controlling the mechanical response. For earthquakes occurring across zones of low porous medium compressibility (< 10−9 Pa−1) and permeability (< 10−18 m2) the characteristic time for thermal pressurization is small. In this case, frictional heating can cause fluid pressures to approach lithostatic values, the shear strength to approach zero, and the temperature rise to stabilize at a maximum value dependent on the pore dilatational and transport properties of the porous medium. Whether the patch acts as a barrier to slip or exhibits substantial strain weakening is dependent on the shear strain across the fault. Moderate slip events where shear strains exceed two cause substantial strain weakening and, consequently, large stress drops, accelerations, and displacements. Thus it is possible for the patch to act as a barrier for small earthquakes but not for large ones. Both the dynamic stress drop and total displacement decrease for zones with larger compressibility, permeability, or width. If the compressibility or permeability exceeds 10−8 Pa−1 or 10−14 m2 or the shear strain is less than one, then the effects of frictional heating may be negligible and the fault will exhibit no strain-weakening characteristics. Consequently, the patch acts as barrier that halts or resists further fault motion. Extrapolation of these results suggests that spatial variations in fault width and hydraulic characteristics will cause a heterogeneous stress drop and fault slip over the failure surface, explaining many of the features of active faulting (e.g., barriers, nonuniform slip, rupture stoppage, random ground accelerations, strong motions, and frequency-magnitude relations).

251 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20242
20234,903
202210,233
20211,417
2020998
2019966