Focal mechanisms and depths of earthquakes in central Pakistan: A tectonic interpretation

Abstract

Focal mechanisms and depths for seven earthquakes in central Pakistan were determined from an analysis of Rayleigh waves of 20‐to 50‐s periods. In east‐central Pakistan, the nodal planes for some solutions strike obliquely to the grain of surface structures. This observation supports the contention of other workers that a thin surficial unit, decoupled from the basement along a surface of decollement, characterizes this region. In west‐central Pakistan, relative movement between the Indian and Eurasian plates is at least partially accommodated by seismic slip along the Chaman fault. Other faults, which are situated to the east of and lie subparallel to the Chaman fault, may also take up some of the relative plate motion. Observed activity within the zone of convergent‐type structure in central Pakistan may be a result of the greater component of convergence across the Indian‐Eurasian plate boundary north of Quetta, Pakistan.Appendix is available with entire article on microfiche. Order from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, D.C. 20009. Document B83‐010; $2.50. Payment must accompany order.