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Determination of earthquake focal depths and source time functions in central Asia using teleseismic P waveforms
Author(s) -
Chu Risheng,
Zhu Lupei,
Helmberger Don V.
Publication year - 2009
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2009gl039494
Subject(s) - geology , seismology , focal mechanism , subduction , crust , moment tensor , deconvolution , geothermal gradient , waveform , receiver function , aftershock , centroid , geodesy , geophysics , induced seismicity , tectonics , lithosphere , geometry , deformation (meteorology) , radar , telecommunications , oceanography , algorithm , computer science , mathematics
We developed a new method to determine earthquake source time functions and focal depths. It uses theoretical Green's function and a time‐domain deconvolution with positivity constraint to estimate the source time function from the teleseismic P waveforms. The earthquake focal depth is also determined in the process by using the time separations of the direct P and depth phases. We applied this method to 606 earthquakes between 1990 and 2005 in Central Asia. The results show that the Centroid Moment Tensor solutions, which are routinely computed for earthquake larger than M 5.0 globally using very long period body and surface waves, systematically over‐estimated the source depths and durations, especially for shallow events. Away from the subduction zone, most of the 606 earthquakes occurred within the top 20 km of crust. This shallow distribution of earthquakes suggests a high geotherm and a weak ductile lower crust in the region.