Susumu Kurahashi

Source model of the 2007 Noto-Hanto earthquake (Mw 6.7) for estimating broad-band strong ground motion

A source model for estimating broad-band ground motions from the 2007 Noto-Hanto earthquake (Mw 6.7) is estimated from a comparison of the observed records of the mainshock and synthesized motions based on the characterized asperity model using the empirical Green’s function method. The observed records of aftershocks used as the empirical Green’s functions are carefully selected to have almost the same radiation characteristics and source distance as the asperities of the mainshock. The best-fit source model consists of two asperities of different size. A large one is located just above the hypocenter, with an area of 6.3×6.3 km2 and stress drop of about 26 MPa. A smaller one is located north-east of the large one, with an area of 3.6×3.6 km2 and stress drop of about 10 MPa. The stress drop of the large one is about twofold higher than the average values of inland crustal earthquakes so far estimated, while that of smaller one is almost average. We found that the remarkable directivity pulses from the source model struck the northern part of the Noto peninsula, causing heavy damage in some towns there.

Nonlinear Response Potential of Real versus Simulated Ground Motions for the 11 March 2011 Tohoku-oki Earthquake

This study compares the nonlinear response potential of generic inelastic single-degree-of-freedom systems subjected to three sets of ground motion records for the 2011 Tohoku main shock. The compared record sets, all for the same sites, are: (1) observed accelerograms at 48 KiK-net strong motion stations; (2) time-histories simulated from the empirical Greens function method; and (3) time-histories simulated using the stochastic finite-fault method (with multiple sub-events). The adopted techniques can capture a realistic source rupture process involving multiple strong motion generation areas in simulations. Statistical analysis of computed peak ductility demands for the three record sets is conducted via cloud and stripe analyses. Results indicate that for the 2011 Tohoku main shock, different record sets produce similar average trends of the inelastic seismic demand curves. This conclusion is applicable to both cloud and stripe approaches and to structural systems with degrading and pinching hysteresis.

AN EVALUATION MODEL OF MEDICAL TRANSPORT WITH TSUNAMI EARLY WARNING SYSTEM

The Japanese Central Disaster Management Council announced a new damage estimate in the event of an earthquake with its epicenter in the Nankai Trough. The estimate shows the huge human damage. However, they mentioned the possibility of minimizing the casualty count by constant preparation for prompt evacuation to higher places in the event of a tsunami. This study aims to develop a reliability analysis model for medical transport activity considering a tsunami risk. The model includes a risk evaluation model developed to evaluate medical transport activity when a tsunami early warning system can be used. By applying it to Chita Peninsula in Japan, it is demonstrated that the proposed model effectively implements the evacuation and medical transport planning. Some proposals are given for the road network in the area.

Field experiment report for exploration of abandoned lignite mines with teleinvestigation robot system

The risk of collapse and subsidence of the abandoned lignite mines has been mentioned in Tokai region of Japan. The filling of the cavity is still being advanced. There is no cavity map in the abandoned lignite mines, and it is required to grasp and explore of the underground space in order to estimate the amount of the filling material. By a request from Mitake-cho in Gifu Prefecture, we got the opportunity to explore the inside of an abandoned lignite mine by using our robot system. Prior to the exploration of the actual abandoned lignite mine, as feasibility study, an experimental test field that simulated the elements of abandoned lignite mine was prepared in outdoor. Some experimentations were performed and the explore robot system was evaluated in this study. This paper described about the lessons learned from the feasibility study.

TSUNAMI-GENERATION WARNING SYSTEM USING EARTHQUAKE EARLY WARNING

We propose early-warning system for reducing tsunami refuge using the data of the magnitude and the depth informed by the Earthquake Early Warning (EEW) by Japan Metrological Agency (JMA). The EEW provides advance announcement of the estimated seismic intensity and expectSed arrival time at the just points and regions before arriving strong motion. The hypocenter and magnitude of the earthquake are estimated by using wave form data observed by seismographs near the epicenter. Inukai et al. (2009) proposed the method to determine whether generate tsunami using scaling relation between magnitude and depth of hypocenter. The probability of tsunami generating is calculated by using the EEW information (magnitude and depth) and the Inukai’s scaling relations. In this method, the information of probability of tsunami generating is issued in a few seconds after EEW. We incorporated this method into our system and verified validity of our system.