Precursory seismic quiescence before theM_w= 8.3 Tokachi-oki, Japan, earthquake on 26 September 2003 revealed by a re-examined earthquake catalog

Abstract

[1] The 2003 Tokachi-oki earthquake (M w = 8.3) occurred on 26 September 2003 off the pacific coast of Hokkaido, Japan. In the present study, an earthquake catalog is used that lists 2,000 earthquakes with M ≥ 3.3. All of the earthquake waveforms were recorded by the Institute of Seismology and Volcanology, Hokkaido University. In the present study, these waveforms are manually re-examined, and hypocenters and magnitudes are re-calculated. A detailed analysis of the re-determined earthquake catalog between 1994 and 2003 using a gridding technique (ZMAP) shows that the 2003 Tokachi-oki earthquake is preceded by two neighboring seismic quiescence anomalies that start around the beginning of 1999, and last about 5 years, until the main shock occurs. These quiescence anomalies are located around the asperity ruptured by the main shock, and the Z-values are +3.9 and +4.0 for a time window of T w = 4 years, using a sample size of N = 100 earthquakes. The detected seismic quiescences can be interpreted as being caused by a decrease of 50% in the stressing rate based on Dieterich's theory. It is proposed that a quasi-static pre-slip occurs at the northeastern edge of the asperity ruptured by the main shock, and lasts for five years until the main shock occurs. By calculating the change in the Coulomb failure stress (DCFS), it is found that negative DCFS areas are consistent with the two quiescence anomalies, and a positive DCFS area corresponds to the hypocenter of the main shock, indicating that the quasi-static pre-slip model is a plausible one.

Long-Term Seismic Quiescences and Great Earthquakes in and Around the Japan Subduction Zone Between 1975 and 2012

“…The quiescence area includes the epicenter of the main shock and overlaps with the asperity ruptured by the 2003 event. The seismic quiescence followed by the 2003 Tokachi-oki earthquake (M w 8.3) has been reported by Takahashi and Kasahara (2004) and Katsumata (2011a). The duration time of the seismic quiescence is found to be 9.8 years in this study, which is consistent with Takahashi and Kasahara (2004).…”

“…3:3 in a re-determined earthquake catalog between 1994 and 2003 and found that the duration time of the seismic quiescence was 5 years before the 2003 main shock. The earthquake catalog used by Katsumata (2011a) was too short to identify the long-term seismic quiescence during 9.8 years, thus it is not clear whether the results in Katsumata (2011a) are consistent with those in this study. Area the area numbers are the same as those shown in Fig.…”

“…5:0 in the JMA catalog from 1952 to 2003 and they obtained the same results as those in this study even if they used the JMA catalog and they did not apply the declustering process. Katsumata (2011a) analyzed earthquakes with M ! 3:3 in a re-determined earthquake catalog between 1994 and 2003 and found that the duration time of the seismic quiescence was 5 years before the 2003 main shock.…”

“…Takahashi and Kasahara (2004) recognized that the seismicity rate decreased in the early 1990s in and around the source volume of the 2003 Tokachi-oki earthquake. Katsumata (2011a) found that the seismic quiescence started 5 years before the 2003 main shock within the Pacific slab subducting beneath the continental plate and suggested that the seismic quiescence was caused by the local stress drop due to a precursory quasi-static pre-slip on the plate boundary. Wyss and Habermann (1979) expressed an intermediate-term earthquake prediction based on the seismic quiescence identified: the location is 45.5°-49.2°N and 153°-155°E, the length of the seismic fault is from 200 to 400 km, that is, the magnitude is larger than 8.0, and the occurrence time is from 1979 to 1994.…”

Inhomogeneous precursor characteristics of rock with prefabricated cracks before fracture and its implication for earthquake monitoring

“…Some researchers find that there may be an acceleration period of seismic activity rather than the quiescence before some violent earthquakes (Bowman and King, 2001;Chen, 2003). However, with the development of seismic monitoring methods and the improvement of earthquake catalogue, more and more phenomena of quiescence before large earthquakes have been found (Wu and Chiao, 2006;Katsumata, 2011;Pu, 2018). The relationship between accelerating seismicity and quiescence is also highly regarded, as they are two major phenomena ahead of a main shock (Di Giovambattista and Tyupkin, 2004;Mignan and Di Giovambattista, 2008).…”