Earthquake focal mechanisms, moment tensors, and the consistency of seismic activity near plate boundaries

Article Abstract:

Moment tensor analysis of some 8,000 earthquakes is used to define source and other characteristics of shallow earthquakes. A measure of the similarity of earthquakes in a group is introduced and used in consonance with triangle diagrams to describe movements within 200 km of subduction and ridge-form plate boundaries. The results indicate variable quake mechanisms, high similarity of quakes near such boundaries, and fault slip deformation patterns are the rule for group quakes. Moment is produced most efficiently by thrust earthquakes along subduction zones.

Analysis, Observations, Earthquakes, Seismology, Earthquake intensity

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Extensional reactivation of the Chocolate Mountains subduction thrust in the Gavilan Hills of Southeastern California

Article Abstract:

The extensional reactivation of the Chocolate Mountains subduction thrust in the Gavilan Hills of Southeastern California was examined to provide new evidence to determine the normal fault involved in the uncovering of the schist. The research utilized a detailed structural analysis of a zone of deformation at the top of the Orocopia Schist. Results reveal that the approximate parallelism of foliation and the convergence of metamorphic conditions prove that the Chocolate Mountains fault was a burial fault.

Formations (Geology), Geological formations

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Seven million years of strike-slip and related off-fault deformation, northeastern Marlborough fault system, South Island, New Zealand

Article Abstract:

A study was conducted on the strike-slip and off-fault deformations in the Marlborough fault system, South Island, New Zealand. The spatial and temporal strike slip patterns in the fault system indicate the southward migration of transform motion caused by convergence of the Pac-Aus plates. Results also suggest a simple mechanical relationship between slip partitioning and subduction interface.

New Zealand, Natural history

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