No. 1109

Title:

Preseismic anomalies in seismicity and crustal deformation: Case studies of the 2007 Noto Peninsula Earthquake of M6.9 and the 2007 Chuetsu-Oki Earthquake of M6.8

Author(s):

Ogata, Yosihiko (Institute of Statistical Mathematics and Graduate University of Advanced Studies)

Key words:

aseismic slips, Coulomb failure stress, epidemic type aftershock sequence (ETAS) model, GPS geodetic records

Abstract:

    If aseismic slip occurs on a fault or its deeper extension, both seismicity and crustal deformation around the source would be affected. Anomalies of this type are determined from earthquake occurrence data and geodetic records during the periods leading up to the March 2007 Noto Peninsula Earthquake of M6.9 and the July 2007 Chuetsu-Oki Earthquake of M6.8, which occurred in succession on the Japan Sea coast. Assuming such aseismic slips, seismic zones corresponding to negative and positive increments of the Coulomb failure stress show seismic quiescence and activation, respectively, relative to the rate predicted by the epidemic type aftershock sequence (ETAS) model. These interpretations are further supported by transient crustal movements around the sources preceding the ruptures, i.e., the time series of baseline distances between permanent Global Positioning System (GPS) stations deviated from their long-term linear trends in a manner that is basically consistent with the assumed slip.