10:45 AM - 12:15 PM
[SSS10-P07] Fluctuation of b-value around Wakayama Prefecture using JMA's earthquake data
Keywords:b-value, Gutenberg-Richter law, Wakayama Prefecture
Variations in the b-value may indicate changes in the surrounding crustal stress field and are possibly beneficial for earthquake prediction. Previous studies showed that the b-value decreased in the source region before the 2004 Sumatra earthquake and 2011 off the Pacific coast of the Tohoku earthquake. However, the timing and pattern of the b-value fluctuation differ in different regions and earthquakes, and earthquake prediction based on b-values is a long way from a practical level. We analyzed b-value fluctuation using earthquake data from the Japan Meteorological Agency (JMA) around Wakayama Prefecture to understand the trend of b-value fluctuation during large earthquakes and contribute to improving the accuracy of earthquake prediction.
The JMA's earthquake data is from 1919. However, we used data after 1975 because there was not enough data on earthquakes of M3 class or less before that. The analysis area was set around Wakayama Prefecture, where seismic activity is active, with Mc of 2.5. The major earthquakes that occurred near the area during the analysis period are 1984 off the southeast coast of Mie Prefecture (M7.0), the 1995 earthquake in southern Hyogo Prefecture (M7.3), and the 2004 earthquake off the southeast coast of the Kii Peninsula (M7.1). The b-values in this study varied between 0.7 and 1.3, but no common characteristic variation was confirmed related to the above earthquakes. The selection of the analysis area might be inappropriate. In this study, although we focused on the area around Wakayama Prefecture because of high seismicity, this analysis area is away from the source region of the investigated earthquakes. We did not include the earthquake's foreshock and aftershock activities, which likely impact the b-value estimations. Therefore, we will analyze the b-value fluctuation near the earthquake source regions for the next step.
The JMA's earthquake data is from 1919. However, we used data after 1975 because there was not enough data on earthquakes of M3 class or less before that. The analysis area was set around Wakayama Prefecture, where seismic activity is active, with Mc of 2.5. The major earthquakes that occurred near the area during the analysis period are 1984 off the southeast coast of Mie Prefecture (M7.0), the 1995 earthquake in southern Hyogo Prefecture (M7.3), and the 2004 earthquake off the southeast coast of the Kii Peninsula (M7.1). The b-values in this study varied between 0.7 and 1.3, but no common characteristic variation was confirmed related to the above earthquakes. The selection of the analysis area might be inappropriate. In this study, although we focused on the area around Wakayama Prefecture because of high seismicity, this analysis area is away from the source region of the investigated earthquakes. We did not include the earthquake's foreshock and aftershock activities, which likely impact the b-value estimations. Therefore, we will analyze the b-value fluctuation near the earthquake source regions for the next step.