Himalayan Geology, Vol. 32
(2), 2011, pp. 149-157, Printed in India
Source Mechanism studies around Karakorum fault in Siachen region, NW
AJAY PAUL1*, KAMAL2, A. GANJU3, V.RANA1,
D.K.TYAGI1, VIKAS JUYAL3, M. GOSAIN3, N. THAKUR3
1Wadia Institute of Himalayan Geology, Dehradun – 248001, India
2Indian Institute of Technology, Roorkee – 247667, India
3Snow and Avalanche Study Establishment, Chandigarh - 160036,
Abstract: Analysis of fault plane solutions of earthquakes is carried out in
most seismotectonic studies to characterize the tectonic deformation styles
and to estimate strain and stress directions in the investigated areas. 35
seismic events with coda magnitude (MC) 0.3 to 4.2 were chosen from data
recorded by four Broad Band Seismographs and one accelerograph deployed in
Siachen region of NW Himalaya (India). These events were recorded from
seismic network in the vicinity of eastern Karakorum from June 2008 to June
2009. We determined composite fault plane solutions for these 35 earthquake
events from the study of first P-wave motion. Analysis of spatial
distribution shows that focal depth of the events in shallow crust < 15 km,
intermediate deep crust (40-63 km) and mantle events > 90 km is not uniform.
The events can be grouped for depth <15 and in depth range 40-63 km in the
intermediate crust. Two faults mechanism solutions in the western and
eastern segments of Karakorum fault (KF) shows major thrust faults with
small strike slip component. The fault planes of thrust faulting earthquakes
are oriented in NW-SE direction based on analyses of stereonet diagrams of
fault plane solutions. Thus two retrieved fault plane solutions agree with
the geometrical trend of known surface faults across the Karakorum fault.
The seismicity plot suggests that the activity is more pronounced in a
narrow range cutting across Karakorum fault at 34°N.
Key words: Earthquake, Karakorum, fault plane solution.