Open AccessA broad 660 km discontinuity beneath northeast China revealed by dense regional seismic networks in China
Author(s) -
Wang Baoshan,
Niu Fenglin
Publication year - 2010
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009jb006608
Subject(s) - geology , seismology , seismogram , discontinuity (linguistics) , slab , mantle (geology) , china , waveform , transition zone , p wave , front (military) , geophysics , geodesy , physics , medicine , mathematical analysis , mathematics , quantum mechanics , voltage , oceanography , political science , law , cardiology , atrial fibrillation
We examined the P wave velocity structure around the 660 km discontinuity at the tip of the subducting Pacific slab beneath northeastern China by forward modeling waveform triplication data. A total of 742 broadband seismograms were recorded by dense regional seismic networks in China from a deep earthquake that occurred near the border of east Russia and northeast China, providing an unprecedented density of ray coverage near the front edge of the subducting Pacific slab. Multiple P waves were observed on single seismograms in the distance range of ∼14°–29°. The P wave triplication shows the following two features: (1) the direct arrival traveling above the 660 km discontinuity (AB branch) extends as far as ∼29°, approximately 6° further than the prediction from velocity model of International Association of Seismology and the Physics of the earth's interior (iasp91); (2) the refracted wave propagating through the lower mantle (CD branch) appears at a distance a few degrees greater than that of the iasp91 synthetics. Forward waveform modeling suggests that they are best explained by a high‐velocity transition zone underlain by a ∼50–70 km thick 660 km discontinuity. The broadened discontinuity is likely caused by multiple phase transitions associated with the dissolutions of olivine and garnet components.