10:45 AM - 12:15 PM
[SSS10-P03] Earthquake swarm occurring in Noto Peninsula (2)
Keywords:seismic swarm in the Noto Peninsula, moment tensor solution
Seismicity has been active since June, 2018 in northern Noto peninsula. This seismic swarm has four clusters in the north, east, west, and south. The seismic activity started in the south cluster, and the active area expanded to the west, north, and east. We investigated moment tensors of the earthquakes with data of short-period seismometers. After the correction of instrumental responses, band-pass filter of 4-8 sec was applied. Theoretical records were calculated with the method of Takeo (1985).
Some moment tensor solutions of the events in the north, east, and west were estimated. However solutions for events in the south cluster were not obtained due to their small sizes. Many of the solutions were of reverse fault type with east-west compression axis, which would reflect the regional stress of this area. It is inferred that the some kind of fluid is related to this seismic activity, because continuous crustal deformation has been observed in this non-volcanic area.
Based on these observations, we assume that this earthquake swarm is occurring under the situations described below (see Figure). It is considered that regional stress in this area has been supported by the crust around the north and east clusters. Fluid from lower crust or upper mantle intruded around the south cluster area where the regional stress was relatively low compared with northern areas. It was the start of the earthquake swarm activity. Then supply of fluid from deep crust continued, and it intruded into the northern area of the south cluster. The fluid into the existing cracks decreased the frictional force which had been supported the regional stress, and a number of earthquakes occurred by the regional stress of east-west compression.
Acknowledgements: We used the data provided by the Japan Meteorological Agency with the cooperation of the Ministry of Education, Culture, Sports, Science and Technology of Japan based on data from NIED, Hokkaido University, Hirosaki University, Tohoku University, The University of Tokyo, Nagoya University, Kyoto University, Kochi University, Kyushu University, Kagoshima University, the National Institute of Advanced Industrial Science and Technology, the Geospatial Information Authority of Japan, the Japan Agency for Marine-Earth Science and Technology, the Association for the Development of Earthquake Prediction, the Incorporated Research Institutes for Seismology, the Japan Meteorological Agency, and the governments of Aomori Prefecture, the Tokyo Metropolitan Government, Shizuoka Prefecture, and Kanagawa Prefecture. We used seismic records downloaded from the NIED repository.
Some moment tensor solutions of the events in the north, east, and west were estimated. However solutions for events in the south cluster were not obtained due to their small sizes. Many of the solutions were of reverse fault type with east-west compression axis, which would reflect the regional stress of this area. It is inferred that the some kind of fluid is related to this seismic activity, because continuous crustal deformation has been observed in this non-volcanic area.
Based on these observations, we assume that this earthquake swarm is occurring under the situations described below (see Figure). It is considered that regional stress in this area has been supported by the crust around the north and east clusters. Fluid from lower crust or upper mantle intruded around the south cluster area where the regional stress was relatively low compared with northern areas. It was the start of the earthquake swarm activity. Then supply of fluid from deep crust continued, and it intruded into the northern area of the south cluster. The fluid into the existing cracks decreased the frictional force which had been supported the regional stress, and a number of earthquakes occurred by the regional stress of east-west compression.
Acknowledgements: We used the data provided by the Japan Meteorological Agency with the cooperation of the Ministry of Education, Culture, Sports, Science and Technology of Japan based on data from NIED, Hokkaido University, Hirosaki University, Tohoku University, The University of Tokyo, Nagoya University, Kyoto University, Kochi University, Kyushu University, Kagoshima University, the National Institute of Advanced Industrial Science and Technology, the Geospatial Information Authority of Japan, the Japan Agency for Marine-Earth Science and Technology, the Association for the Development of Earthquake Prediction, the Incorporated Research Institutes for Seismology, the Japan Meteorological Agency, and the governments of Aomori Prefecture, the Tokyo Metropolitan Government, Shizuoka Prefecture, and Kanagawa Prefecture. We used seismic records downloaded from the NIED repository.