Fault (geology)

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

Tectonics of the Andaman Sea and Burma: Convergent Margins

Abstract: The Andaman-Nicobar Ridge and the Indo-Burman Range are composed of sediments of the Bengal and Nicobar Fans scraped off the underthrusting Indian plate at the Sunda subduction zone. The Andaman Sea and the eastern part of the central valley of Burma represent a Neogene-Quaternary extensional basin underlain by oceanic crust formed by northwestward rifting of this orogenic ridge away from continental crust of the eastern Burma highlands and the Malay Peninsula. The plate edge is defined by a north-south transform in Burma, by the Sumatran fault system longitudinally bisecting Sumatra, and by a complex system of short spreading rifts and transforms in the central basin of the Andaman Sea. Where sedimentation rates are high over the newly formed oceanic crust, no magnetic a omalies are identifiable; where sedimentation rates are low or negligible, clear magnetic anomalies have permitted dating this phase of opening at approximately 11 m.y. B.P.

Geologic factors controlling patterns of small‐volume basaltic volcanism: Application to a volcanic hazards assessment at Yucca Mountain, Nevada

Abstract: The proposed high-level radioactive waste repository at Yucca Mountain, Nevada, is located within an active volcanic field. Probabilistic volcanic hazard models for future eruptions through the proposed repository depend heavily on our understanding of the spatial controls on volcano distribution at a variety of scales. On regional scales, Pliocene-Quaternary volcano clusters are located east of the Bare Mountain fault. Extension has resulted in large-scale crustal density contrast across the fault, and vents are restricted to low-density areas of the hanging wall. Finite element modeling indicates that this crustal density contrast can result in transient pressure changes of up to 7 MPa at 40 km depth, providing a mechanism to generate partial melts in areas where mantle rocks are already close to their solidus. On subregional scales, vent alignments, including one alignment newly recognized by ground magnetic mapping, parallel the trends of high-dilation tendency faults in the Yucca Mountain region (YMR). Forty percent of vents in the YMR are part of vent alignments that vary in length from 2 to 16 km. Locally, new geological and geophysical data show that individual vents and short vent alignments occur along and adjacent to faults, particularly at fault intersections, and left-stepping en echelon fault segments adjacent to Yucca Mountain. Conditions which formed these structures persist in the YMR today, indicating that volcanism will likely continue in the region and that the proposed repository site is within an area where future volcanism may occur. On the basis of these data the probability of volcanic disruptions of the proposed repository is estimated between 10−8/yr and 10−7/yr.

Magnitude of post–Middle Jurassic (Bajocian) displacement on the central Altyn Tagh fault system, northwest China

Abstract: The Altyn Tagh fault system, a key structural feature in the tectonic collage of central Asia, is an active left-lateral strike-slip fault system. However, its age of initiation, kinematic history, and total magnitude of displacement are not well known. Middle Jurassic nonmarine sedimentary rocks that crop out along the central segment of the Altyn Tagh fault were deposited in a contiguous Tarim-Qaidam foreland-style basin that was geodynamically linked to Mesozoic contraction in the Tian Shan, Bei Shan, Qilian Shan, and Kunlun Shan. This study documents the best evidence of a piercing point to date, consisting of an offset lacustrine shoreline demarcated by Aalenian-Bajocian open lacustrine strata to the west and fluvial and alluvial strata of comparable age to the east. Detrital compositions, palynology, paleocurrents, and lithostratigraphy support correlation of these sections. Restoration of this Jurassic facies boundary indicates 400 ± 60 km of post-Bajocian left-lateral separation on the Altyn Tagh fault. Consistent with this result, restoration of the Jurassic shoreline aligns felsic plutons across the western segment of the Altyn Tagh fault system that may have been left-laterally offset by 360 km. These two pairs of offset features suggest that the current best estimate for net magnitude of post-Bajocian left-lateral separation on the Altyn Tagh fault is about 360 km.