TY - JOUR
T1 - Centroid-moment-tensor solutions for deep earthquakes predating the digital era
T2 - discussion and inferences
AU - Huang, Wei Chuang
AU - Okal, Emile A.
N1 - Funding Information:
The inversion of the predigital CMT solutions was carried out in collaboration with Harvard University, and we thank Göran Ekström and Misha Salganik for their valuable help over several years. We acknowledge many discussions with Steve Kirby, Craig Bina and Seth Stein. Robin Adams kindly attempted to relocate the 1907 Sea of Okhotsk earthquake. Many figures were drafted using the GMT software ( Wessel and Smith, 1991 ). We are grateful to Cliff Frohlich for a careful review. This research was supported by the National Science Foundation under grant EAR-93-16396.
PY - 1998/4/10
Y1 - 1998/4/10
N2 - We present a discussion of 139 new centroid-moment-tensor solutions for deep earthquakes covering the WWSSN (1962-1976) and earlier years, obtained by applying the standard Harvard inversion algorithm to data sets of seismograms digitized from analog records. Our solutions fill several gaps in seismicity reflecting undersampling by the Harvard catalogue. While most focal mechanisms previously published for WWSSN-era earthquakes are in good agreement with our inverted solutions, focal geometries for older events appear unreliable. We confirm that the region of most intense moment release is around 650 km, and that a minimum exists at 500 km. However, the local maximum around 450 km may be less marked than previously suggested. The Bonin-Marianas subduction zone exhibits a different pattern with an overall maximum of seismic activity at 420 km. All other subduction zones demonstrate the potential for seismicity at least at the 1027 dyn-cm level. Finally, while non-double-couple components are found systematically in our enhanced data set, they correlate neither with depth nor with earthquake size, suggesting that their presence does not necessarily relate to the exiguity of the space available for rupture at the tip of subduction zones.
AB - We present a discussion of 139 new centroid-moment-tensor solutions for deep earthquakes covering the WWSSN (1962-1976) and earlier years, obtained by applying the standard Harvard inversion algorithm to data sets of seismograms digitized from analog records. Our solutions fill several gaps in seismicity reflecting undersampling by the Harvard catalogue. While most focal mechanisms previously published for WWSSN-era earthquakes are in good agreement with our inverted solutions, focal geometries for older events appear unreliable. We confirm that the region of most intense moment release is around 650 km, and that a minimum exists at 500 km. However, the local maximum around 450 km may be less marked than previously suggested. The Bonin-Marianas subduction zone exhibits a different pattern with an overall maximum of seismic activity at 420 km. All other subduction zones demonstrate the potential for seismicity at least at the 1027 dyn-cm level. Finally, while non-double-couple components are found systematically in our enhanced data set, they correlate neither with depth nor with earthquake size, suggesting that their presence does not necessarily relate to the exiguity of the space available for rupture at the tip of subduction zones.
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U2 - 10.1016/S0031-9201(97)00111-8
DO - 10.1016/S0031-9201(97)00111-8
M3 - Article
AN - SCOPUS:0345515975
SN - 0031-9201
VL - 106
SP - 191
EP - 218
JO - Physics of the Earth and Planetary Interiors
JF - Physics of the Earth and Planetary Interiors
IS - 3-4
ER -