11:00 AM - 1:00 PM
[MIS22-P02] Analysis of Aftershock Activity of the 1855 Ansei-Edo Earthquake Using Historical Data in and Around the Kanto Region
Keywords:1855 Ansei Edo earthquake, Aftershock activity
The details of the aftershock activity of the 1855 Ansei Edo earthquake are examined. There are relatively large number of historical records for the 1855 Ansei Edo earthquake. Thus, the frequency of occurrence, the felt area, and the possible locations and magnitudes of the sources can be estimated. Here, larger number of felt data or intensity data points (IDPs) obtained from historical documents of Edo and the Kanto region are examined.
The temporal variation of number of aftershocks are examined for Edo and Chiba. The decrease of the aftershock activity is well modeled by the Omori-Utsu formula. The difference in total number of aftershock and rate of decrease observed for different place can be explained by incompleteness of records of the historical documents. Comparison with the standard aftershock sequence suggests that the temporal variation of aftershocks of the 1855 Ansei Edo earthquake has the characteristics of the intraplate earthquakes.
From an updated catalog of IDPs of aftershocks based on published collections and database of historical earthquake documents, 10 aftershocks are selected for analyses of the size and location. The largest aftershock of the Ansei-Edo earthquake is the event occurred after sunset on November 16.To estimate the size and location of aftershocks, distribution IDPs of aftershocks are compared with observations of seismic intensity distributions for modern earthquakes. The magnitude of the largest aftershock is considered to be larger than that of the July 23, 2005, M_JMA=6.0 earthquake. For the 8 earthquakes that are thought to have occurred in the source region of the Ansei Edo Earthquake, we found that the magnitude of each earthquake was around 4 to 6. The earthquake of November 15, 1855, at around 10:00 p.m. has a different distribution of felt records from the mainshock and its largest aftershocks, suggesting that it may not have occurred in the source region of the Ansei-Edo earthquake.
The temporal variation of number of aftershocks are examined for Edo and Chiba. The decrease of the aftershock activity is well modeled by the Omori-Utsu formula. The difference in total number of aftershock and rate of decrease observed for different place can be explained by incompleteness of records of the historical documents. Comparison with the standard aftershock sequence suggests that the temporal variation of aftershocks of the 1855 Ansei Edo earthquake has the characteristics of the intraplate earthquakes.
From an updated catalog of IDPs of aftershocks based on published collections and database of historical earthquake documents, 10 aftershocks are selected for analyses of the size and location. The largest aftershock of the Ansei-Edo earthquake is the event occurred after sunset on November 16.To estimate the size and location of aftershocks, distribution IDPs of aftershocks are compared with observations of seismic intensity distributions for modern earthquakes. The magnitude of the largest aftershock is considered to be larger than that of the July 23, 2005, M_JMA=6.0 earthquake. For the 8 earthquakes that are thought to have occurred in the source region of the Ansei Edo Earthquake, we found that the magnitude of each earthquake was around 4 to 6. The earthquake of November 15, 1855, at around 10:00 p.m. has a different distribution of felt records from the mainshock and its largest aftershocks, suggesting that it may not have occurred in the source region of the Ansei-Edo earthquake.