Earth Planets Space, Vol. 60 (No. 11), pp. 1137-1141, 2008LETTER
Reiko Tajima and Fumiko Tajima
Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University, 1-3-1 Kagami-yama, Higashi-Hiroshima 739-8526, Japan
(Received November 15, 2007; Revised January 15, 2008; Accepted January 30, 2008; Online published November 18, 2008)
The relationship of seismic moment (M0) to corner frequency (fc) of the 2007 Off Mid Niigata prefecture (Chuetsu-oki) earthquake sequence is examined in comparison with that of two other earthquake sequences. The M0-fc relation of this sequence (3.4 ≤ Mw ≤ 6.6) is M0 ∝ fc-3.87, which deviates from M0 ∝ fc-3. The relatively large deviation from fc-3 may reflect the influence of fluids identified in tomographic studies around the source region of the tectonic strain concentration. Moreover, the lower fcs of the small events (3.4 ≤ Mw ≤ 3.8) in this sequence are similar to those of off-main-fault events in the 2004 Mid Niigata prefecture earthquake sequence. The characteristics in the scaling relation may be interpreted in the context of the event locations, which are either on- or off-main faults, and may have implications for the seismogenic conditions.
Key words: The 2007 Off Mid Niigata earthquake, seismic scaling, seismogenic conditions.