Relation Between Stress Drops and Depths of Strong Motion Generation Areas Based on Previous Broadband Source Models for Crustal Earthquakes in Japan [chapter]

Toshimi Satoh, Atsushi Okazaki
2016 Earthquakes, Tsunamis and Nuclear Risks  
To aim at the advancement of strong motion predictions, we develop empirical relations between stress drops on strong motion generation areas (SMGAs) and depths of SMGAs based on previous broadband source models estimated by the empirical Green's function method. A total of 25 source models for 13 crustal earthquakes of Mw from 5.7 to 6.9 in Japan are used in this study. It is found that stress drops on SMGAs for reverse faults are larger than those for strikeslip faults on average. The average
more » ... verage. The average stress drops are 21.2 MPa, 13.3 MPa, and 18.0 MPa for reverse, strike-slip, and all types of faults, respectively. In the derived empirical relation for all types of faults, the stress drops increase by about 1 MPa every 1 km in depth. This depth dependency is similar to the relation between stress drops on asperities and the depths of asperities derived by Asano and Iwata (Pure Appl Geophys, 168:105-116, 2011), and the absolute value is 4 MPa larger than that by Asano and Iwata (Pure Appl Geophys, 168:105-116, 2011). The depth dependency of stress drops for reverse faults is stronger than that for strike-slip faults. The total area of SMGAs is about 0.8 times of the total area of asperities by Somerville et al. (Seismol Res Lett, 70:59-80, 1999). The result can be interpreted by frequency-dependent source radiations, since asperities are estimated from longer-period (>2 s) strong motions than SMGAs, which are mainly estimated from strong motions in the period range from 0.1 to 5 s.
doi:10.1007/978-4-431-55822-4_6 fatcat:mm62xvimfjgylpgya4y4sti3ey