Fault (geology)

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

Tertiary diachronic extrusion and deformation of western Indochina: Structural and 40Ar/39Ar evidence from NW Thailand

Abstract: The Wang Chao and Three Pagodas fault zones cut the western part of the Indochina block and run parallel to the Red River Fault. Evidence of intense ductile left-lateral shear is found in the Lansang gneisses, which form a 5 km wide elongated core along the Wang Chao fault zone. Dating by 40 Ar/ 39 Ar shows that such deformation probably terminated around 30.5 Ma. The Wang Chao and Three Pagodas faults offset the north striking lower Mesozoic metamorphic and magmatic belt of northern Thailand. 40 Ar/ 39 Ar results suggest that this belt suffered rapid cooling in the Tertiary, probably around 23 Ma. These results imply that the extrusion of the southwestern part of Indochina occurred in the upper Eocene-lower Oligocene. It probably induced rifting in some basins of the Gulf of Thailand and in the Malay and Mekong basins. In the Oligo-Miocene, the continuing penetration of India into Asia culminated with the extrusion of all of Indochina along the Ailao Shan - Red River fault. This occurred concurrently with the onset of E-W extension more to the south. Plotting in a geographical reference frame the diachronic time spans of movement on left-lateral faults east and southeast of Tibet implies that the northward movement of the Indian indenter successively initiated new strike-slip faults located farther and farther north along its path.

Earthquake frequency distribution and the mechanics of faulting

Abstract: The level of intraplate seismicity in Japan generally shows a positive correlation with the density of Quaternary faulting. In southwest Japan, where intraplate seismicity is concentrated on land, rates of seismic moment release ( M˙0) are similar when calculated from either the 400-year historical record of seismicity or geologically determined slip rates of Quaternary faults. A data set of 18 earthquakes with seismic moments (M0) ranging from ∼0.01 to 3×1027 dyn cm shows a relationship between rupture lengthl and M0(log M0 = 23.5+1.94 · log l). When seismic moment on each Quaternary fault is assumed to occur in discrete events every T = M0/ M˙0g years (where M0 is estimated for a rupture extended over the entire fault length, and M˙0g is proportional to the slip rate of each Quaternary fault), the moment frequency distribution of earthquakes (log N =A − B · log M0) predicted from the geologic record is virtually identical to that seen with the 400-year record of seismicity. In contrast, if it is assumed that earthquakes on each fault occur according to the Gutenberg-Richter relation, we obtain poor agreement with the observed seismicity. Thus, while regional seismicity satisfies the relation log N =A − B · log M0 (or equivalently, log N = a − b · log M, where M is magnitude), it appears that seismicity on individual faults does not. This further implies that the primary factor that leads to the magnitude frequency distribution in regional seismicity studies is the relative distribution of the slip rates and lengths of preexisting faults.

Lamprophyre dike intrusion and the age of the Alpine fault, New Zealand

Abstract: The orientations of intrusive rocks from a carbonatitic lamprophyre dike swarm and the history of emplacement relative to country-rock schist structures are compatible with intrusion into tension fractures and Riedel shears formed during initiation of the dextral wrench system of the Alpine fault. New U-Pb and Rb-Sr dates indicate a late Oligocene-early Miocene time of intrusion which, in turn, suggests a mid-Tertiary history for propagation of the Alpine fault plate boundary through South Island, New Zealand.

Coseismic fault rupture at the trench axis during the 2011 Tohoku-oki earthquake

Abstract: Subduction zone models often assume that the shallowest part of the plate interface slips aseismically. Images of the subduction trench next to the Tohoku-oki epicentre, captured using seismic reflection data 11 days after the 2011 earthquake, reveal deformation structures in sediments next to the trench, indicating that fault slip did reach the sea floor.