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 article, a high-resolution image of stress orientation in southern California based on the inversion of earthquake focal mechanisms is presented, which is used to study the mechanics of faulting in the plate boundary region.
Abstract: We present a new, high spatial resolution image of stress orientation in southern California based on the inversion of earthquake focal mechanisms. We use this image to study the mechanics of faulting in the plate boundary region. The stress field contains significant spatial heterogeneity, which in some cases appears to be a result of the complexity of faulting and in other cases appears to be a cause. Temporal changes in the stress field are also observed, primarily related to major earthquakes. The observed 15° (±10°) rotation of the stress axes due to the 1992 M7.3 Landers mainshock implies that the deviatoric stress magnitude in the crust is low, of the order of 10 MPa. This suggests that active faults in southern California are weak. The maximum principal stress axis near the San Andreas Fault is often at ∼50° to the fault strike, indicating that the shear stress on the fault is comparable to the deviatoric stress. The San Andreas in southern California may therefore be a weak fault in a low-strength crust.
312 citations
TL;DR: The Xianshuihe fault of western Sichuan Province, China is one of the world's most active faults, having produced 4 earthquakes during this century of magnitude ≥7 along a 350-km length of the fault as discussed by the authors.
Abstract: The Xianshuihe fault of western Sichuan Province, China, is one of the world's most active faults, having produced 4 earthquakes during this century of magnitude ≥7 along a 350-km length of the fault. At least 8 such events have occurred since 1725. In the more limited 150-km-long segment including Luhuo and Daofu, major earthquakes in 1904, 1923, 1973, and 1981 (M = 7, 7½, 7.6, 6.9) were associated with overlapping surficial fault ruptures and with individual left-lateral displacements as large as 3.6 m. Field studies indicate that this high degree of activity is typical of the fault's longer-term history. The Holocene left-lateral slip rate on the north-western segment of the fault has been 15 ± 5 mm/yr, decreasing to about 5 mm/yr on its southeastern segment, based on radiometrically dated offset stream-channel and terrace deposits and on offset glacial moraines.
Physiographic features of active faulting are fully as diagrammatic as those of California's San Andreas fault, mainly because of high-altitude preservation and the absence of cultural modification on this eastern margin of the Tibetan Plateau. Detailed en echelon tensional and pushup features resulting from surface ruptures in 1973, 1955, 1923, and 1893 can still be recognized today, and new data have been collected bearing on the offsets and fault-rupture lengths during these and other events.
The locations and magnitudes of historic earthquakes suggest that the characteristic earthquake model may apply to the Xianshuihe fault. Obvious geometric segmentation of the fault has controlled the initiation and termination of ruptures in some events, whereas segmentation control for others remains obscure. Based on the historic record, repeat times estimated from slip rates, and current seismic gaps, two segments are particularly likely sites for M = 7+ earthquakes in the near future: the 65-km-long segment between Daofu and Qianning, and the 135-km-long segment bracketing Kangding. Continuing creep has been documented along some segments of the fault, and this, together with the high degree of activity and other unique attributes, makes the Xianshuihe fault one of the most promising sites in the world for earthquake prediction and hazard-evaluation studies.
311 citations
TL;DR: In this article, the variation of displacement along fifteen traces of minor normal faults was measured in the multilayered Quaternary sediments of Kyushu, Japan, and two distinct types of faults, a cone-shaped L-D pattern (C-type) and mesa-shaped one (M-type), were detected.
311 citations
TL;DR: In this article, the authors derived an analytical expression that relates the shape of a fault in cross-section to its shape of the bedding horizons in its hanging wall block, assuming that the wall deforms by simple shear and that the footwall remains undeformed throughout.
310 citations
TL;DR: In this article, the authors present a model in which the Caribbean plate is an intra-American feature formed along the Caribbean spreading center as opposed to the current model that considers the Caribbean plates as a far-travelled crustal segment that formed in the Pacific region.
310 citations