HR: 1340h
AN: S43A-1041    [Abstracts]
TI: Seismic Scaling Relations for the 2007 Off Mid Niigata Earthquake (Mw6.6) Sequence in Japan in Comparison with Two Other Earthquake (Mw6.6) Sequences
AU: * Tajima, R
EM: re-ko-is-loving-it@hiroshima-u.ac.jp
AU: Tajima, F
EM: fumiko@geol.sci.hiroshima-u.ac.jp
AB: We carried out a spectral ratio analysis using the 2007 Off Mid Niigata prefecture earthquake (OMNE) sequence which occurred in the tectonic region similar to the 2004 Mid Niigata prefecture earthquake (MNE) sequence. The relationship of seismic moment (Mo) vs. corner frequency (fc) estimated for the OMNE sequence in the range of 3.4 ≤ Mw ≤ 6.6 is Mo \propto fc^-3.87 which deviates from Mo \propto fc^-3. The Mo - fc relation of the MNE sequence estimated previously was Mo \propto fc^-3.41. Both of the source areas are located in the region where active thrust faulting, folding, and multi-planar faults are characteristic. However, the aftershock activity is different from each other, that is, the OMNE sequence consists of a small number of aftershocks while the MNE produced a large number of aftershocks including six large events with Mw ≥ 5.5. In the 2005 West Off Fukuoka prefecture earthquake sequence the Mo - fc relation is Mo \propto fc^-3.06, and most of the aftershocks occurred on a single fault. There are low-velocity anomalies around the OMNE and MNE hypocenters determined in some seismic tomography models. The heterogeneous distribution of possible fluids may also be responsible for the deviation from the standard model in the scaling relations. The characteristics of lower fc's or stress drops of the small events of the OMNE sequence in 3.4 ≤ Mw ≤ 3.8 are similar to that of ¡Èoff-main fault¡É events of the MNE sequence. The difference (or variation) of the scaling relation for the small events can be interpreted in context with the event locations, i.e., whether they are on or off the main faults. The comparison of the scaling relationship between the on- and off-main fault events may have implications for seismogenic conditions that also results in different aftershock (or seismic) activity as described above.
DE: 7200 SEISMOLOGY
DE: 7203 Body waves
DE: 7209 Earthquake dynamics (1242)
DE: 7215 Earthquake source observations (1240)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Seismology [S]
MN: 2007 Fall Meeting