Topic
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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TL;DR: In this paper, the authors present new low-temperature thermochronometry to date periods of exhumation associated with Kunlun and Haiyuan faults within the northeastern margin of Tibet.
Abstract: The Tibetan Plateau is a prime example of a collisional orogen with widespread strike-slip faults whose age and tectonic significance remain controversial. We present new low-temperature thermochronometry to date periods of exhumation associated with Kunlun and Haiyuan faulting, two major strike-slip faults within the northeastern margin of Tibet. Apatite and zircon (U-Th)/He and apatite fission-track ages, which record exhumation from ~2 to 6 km crustal depths, provide minimum bounds on fault timing. Results from Kunlun samples show increased exhumation rates along the western fault segment at circa 12–8 Ma with a possible earlier phase of motion from ~30–20 Ma, along the central fault segment at circa 20–15 Ma, and along the eastern fault segment at circa 8–5 Ma. Combined with previous studies, our results suggest that motion along the Haiyuan fault may have occurred as early as ~15 Ma along the western/central fault segment before initiating at least by 10–8 Ma along the eastern fault tip. We relate an ~250 km wide zone of transpressional shear to synchronous Kunlun and Haiyuan fault motion and suggest that the present-day configuration of active faults along the northeastern margin of Tibet was likely established since middle Miocene time. We interpret the onset of transpression to relate to the progressive confinement of Tibet against rigid crustal blocks to the north and expansion of crustal thickening to the east during the later stages of orogen development.
234 citations
TL;DR: A detailed analysis of near-source strong motion and leveling data, together with the results of teleseismic waveform modeling by Westaway and Jackson (1987) and aftershock studies by Deschamps and King (1984), allows a satisfactory kinematic description of the complex normal faulting associated with the magnitude 6.9 Irpinia earthquake as discussed by the authors.
Abstract: A detailed analysis of near-source strong motion and leveling data, together with the results of teleseismic waveform modeling by Westaway and Jackson (1987) and aftershock studies by Deschamps and King (1984), allows a satisfactory kinematic description of the complex normal faulting associated with the magnitude Ms = 6.9, November 23,1980, Irpinia earthquake (southern Italy). The three main rupture episodes, starting at about 0, 20 and 40 s, are here associated with better constrained source parameters than in previous studies. We first evaluated the triggering time for the 11 closest accelerometers by using the well-recorded 40-s strong motion phases. This gave the absolute time and location of the dominant episodes of faulting. The first rupture propagated mainly toward the northwest on a NE dipping normal fault, at a mean velocity close to 3 km/s for about 20 km, and continued 15 km further on smaller subfaults. It was associated with surface breakage in the southeastern part. The second rupture started from the southeastern end of the first rupture, about 18 s after it, and propagated about 20 km toward the southeast on a low-angle normal fault dipping 20°NE. It was associated with secondary faulting on steeper planes reaching the surface. The third and last episode at 39 s nucleated near the first hypocenter, at shallower depth, and the rupture possibly propagated on a 10- to 15-km-long normal fault, striking SE, antithetic to the first activated fault. A clear correlation appears between the strength of the geological formations and the existence of surface breakage and shallow aftershock activity.
233 citations
TL;DR: In this article, the authors used the fractal size distribution of fault displacements in the Viking graben in the North Sea to estimate the cumulative extension of Mesozoic faults in a deformed terrane.
Abstract: Extension estimates based on palinspastic restoration of only the largest faults in a deformed terrane may be significantly deficient due to neglect of "small" faults (i.e., unsampled faults, most of which have smaller displacements than do sampled faults). Small faults individually account for little extension, but there may be large numbers of them. The cumulative extension on small faults can be calculated from the fractal size distributions of fault displacements. Independent extension estimates support the inference from fault population statistics that small faults account for significant amounts of extension. For example, restorations of Mesozoic faults interpreted from seismic reflection profiles across the Viking graben in the North Sea yield extension estimates that are only 40%-75% of independent estimates. The fractal size distribution of fault displacements in the Viking graben is consistent with the hypothesis that the remaining 25%-60% of extension resulted from displacements on small faults.
233 citations
TL;DR: The Indian Ocean tsunami of 2004 resulted from a fault rupture more than 1000 km in length that included and dwarfed fault patches that had broken historically during lesser shocks as discussed by the authors, and such variation in rupture mode, known from written history at a few subduction zones is also characteristic of earthquake histories inferred from geology on the Pacific Rim.
Abstract: Histories of earthquakes and tsunamis, inferred from geological evidence, aid in anticipating future catastrophes. This natural warning system now influences building codes and tsunami planning in the United States, Canada, and Japan, particularly where geology demonstrates the past occurrence of earthquakes and tsunamis larger than those known from written and instrumental records. Under favorable circumstances, paleoseismology can thus provide long-term advisories of unusually large tsunamis. The extraordinary Indian Ocean tsunami of 2004 resulted from a fault rupture more than 1000 km in length that included and dwarfed fault patches that had broken historically during lesser shocks. Such variation in rupture mode, known from written history at a few subduction zones, is also characteristic of earthquake histories inferred from geology on the Pacific Rim.
233 citations
TL;DR: In this article, a finite difference hydrodynamical method with finer grids in shallower water was used to estimate the vertical displacement field of the sea bottom derived from the seismic fault model for each earthquake.
Abstract: Numerical experiments of tsunami generation and propagation are carried out for five earthquakes which occurred off the Pacific coast of the Tohoku and Hokkaido districts. The tsunami sources used in the experiments are the vertical displacement field of the sea bottom derived from the seismic fault model for each earthquake. Water surface disturbances are computed by a finite difference hydrodynamical method with finer grids in shallower water. The comparison of the computed tsunami behavior with available tsunami records along the coast shows that the distribution of observed tsunami heights can be explained in the first approximation by seismic fault models while the observed heights are 1.2 to 1.6 times larger than the computed heights. An example of a fault model inferred from seismic data (June 12, 1968) which is not suitable for a tsunami source is presented.
233 citations