Regional Characterization of the Crust in Metropolitan Areas for Prediction of Strong Ground Motion
Abstract
Introduction: After the 1995 Kobe earthquake, the Japanese government increased its focus and funding of earthquake hazards evaluation, studies of man-made structures integrity, and emergency response planning in the major urban centers. A new agency, the Ministry of Education, Science, Sports and Culture (MEXT) has started a five-year program titled as Special Project for Earthquake Disaster Mitigation in Urban Areas (abbreviated to Dai-dai-toku in Japanese) since 2002. The project includes four programs: I. Regional characterization of the crust in metropolitan areas for prediction of strong ground motion. II. Significant improvement of seismic performance of structure. III. Advanced disaster management system. IV. Investigation of earthquake disaster mitigation research results. We will present the results from the first program conducted in 2002 and 2003. Regional Characterization of the Crust in Metropolitan Areas for Prediction of Strong Ground Motion: A long-term goal is to produce map of reliable estimations of strong ground motion. This requires accurate determination of ground motion response, which includes a source process, an effect of propagation path, and near surface response. The new five-year project was aimed to characterize the "source" and "propagation path" in the Kanto (Tokyo) region and Kinki (Osaka) region. The 1923 Kanto Earthquake is one of the important targets to be addressed in the project. The proximity of the Pacific and Philippine Sea subducting plates requires study of the relationship between earthquakes and regional tectonics. This project focuses on identification and geometry of: 1) Source faults, 2) Subducting plates and mega-thrust faults, 3) Crustal structure, 4) Seismogenic zone, 5) Sedimentary basins, 6) 3D velocity properties We have conducted a series of seismic reflection and refraction experiment in the Kanto region. In 2002 we have completed to deploy seismic profiling lines in the Boso peninsula (112 km) and the Sagami bay area (75 km) to image the subducting Philippine Sea plate. On the Boso line we drilled a hole at a depth of 2000 m with core sampling and logging including VSP. A high sensitivity down hole seismometer will bee installed at the hole. In 2003, a 71-km-long reflection/refraction line covered the Tokyo bay area to characterize the source area of the 1923 Kanto quake. The southern part of the line ran through the Miura peninsula, which was covered by a 20 x 15 km array consisting of 51 3-component continuously recording seismographs to identify the asperities suggested by strong motion studies. We also cover the eastern boundary of the Kanto Mountains in this fall. Reconstruction of source fault and velocity models allow for more realistic 3D seimic wave simulations. All of this information will be synthesized and provided to communities involved in probabilistic hazards analysis, risk assessment and societal response.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2003
- Bibcode:
- 2003AGUFM.S52B0140H
- Keywords:
-
- 1242 Seismic deformations (7205);
- 7223 Seismic hazard assessment and prediction;
- 8010 Fractures and faults;
- 8015 Local crustal structure;
- 8164 Stresses: crust and lithosphere