@inproceedings{oai:kutarr.kochi-tech.ac.jp:00000902,
 author = {Nigauri, Yasuhide and Miyata, Takao},
 book = {Society for Social Management Systems Internet Journal},
 issue = {1},
 month = {Mar},
 note = {An intra-plate earthquake is one of the major threats to mega cities. For the effective earthquake risk management, we need to answer the following questions, when, where, and how large earthquake will occur in the near future. The earthquake occurs along the fault zone. The fault zone is divided into many fault segments. Some of the segments move during the earthquake. It is important to become clear the activities of individual fault segments. Kobe is in the center of the Rokko-Awaji fault zone. The total fault length is 71 km. The fault movements are predominantly right-lateral slip with dip-slip (reverse fault) (HERP, 2005b). And the Osakawan fault zone, having the whole length of 39 km exists in the Osaka bay, south of Kobe. From the length of the fault segment, the magnitude of earthquake can be estimated (e.g. Matsuda, 1975). There are nine active fault segments in a circle of 10 km from the center of Kobe. The average length of the nine segments is 6.6 km. The magnitude of 6.2 is obtained from the Matsuda’s empirical formula. If the earthquake energy was enough to break the single fault segment, the fault movement could propagate to the next segment. This propagation was caused during the 1995 Hyogoken-Nanbu (Kobe) earthquake. There are sixteen active fault segments in the circle of 20 km. When we have chosen two fault segments in the circle of 20 km from Kobe based on a topographical connection, we can imagine the six combinations. Their average length is 19.3 km. From this length, the magnitude of 7.0 is estimated. This magnitude is larger one order than that of single segment. The estimation of the earthquake magnitude from the Headquarter for Earthquake Research indicates simultaneous activity of the fault zone. The large earthquake (M 7 ~ M 8 classes) shakes in a wide area. In the case of the smaller (M 6 class) earthquakes, severe disasters are occurred in the limited area near the epicenters. Generally comparison of the large earthquakes, smaller earthquakes often occur. For the effective earthquake risk management, we need the cost analysis using the proper estimation of the earthquake. It is effective to prepare the large earthquake against the large network and the long-time using institutions, such as roads, bridges, tunnels and plants. On the other hand, for the short-time using and small structures such as buildings and housings, it is more effective to prepare the smaller earthquake.},
 publisher = {Society for Social Management Systems},
 title = {Importance of the Active Fault Researches for Effective Earthquake Risk Management},
 volume = {4},
 year = {2008}
}