Three-dimensional plate geometry and velocity model for the Nankai Trough subduction seismogenic zone based on structural studies

Conerence abstract (AOGS 12th Annual Meeting, August 2-7, 2015, Singapore)http://www.godac.jamstec.go.jp/darwin/cruise/kairei/kr08-16/ehttp://www.godac.jamstec.go.jp/darwin/cruise/kairei/kr09-14/ehttp://www.godac.jamstec.go.jp/darwin/cruise/kairei/kr10-11/ehttp://www.godac.jamstec.go.jp/darwin/cruise/kairei/kr11-09/ehttp://www.godac.jamstec.go.jp/darwin/cruise/kaiyo/ky10-02/

Broadband ground-motion simulation of the 24 May 2014 Gokceada (North Aegean Sea) earthquake (Mw 6.9) in NW Turkey considering local soil effects

On 24 May 2014, a Mw 6.9 earthquake occurred in the west of Gokceada Island, northern Aegean Sea. The earthquake was close to Canakkale, Enez, Tekirdag cities, and damaged 300 buildings in the Marmara Region, NW Turkey. We simulated its broadband (0.1-10 Hz) ground motions including 1D deep and shallow structures soil amplification effects at the 12 strong ground motion stations in the western Marmara Region. The 1D deep velocity structures from the focal layer to the engineering bedrock with an S-wave velocity of 0.78 km/s in different azimuthal directions were tuned by comparing the observed group-velocity dispersion curves of Rayleigh and Love waves from the mainshock with theoretical ones. We also added the shallow parts from previous surveys into the 1D models. Synthetic seismograms on the engineering bedrock were generated using the discrete wave number method with a source model and the 1D deep velocity structures. Then the surface motion was generated considering shallow soil amplification. The synthetic seismograms are generally in good agreement with the observed low and high-frequency parts at most of the stations indicating an appropriateness of the source model and the 1D structural model

Estimation of shallow S-wave velocity structure and site response characteristics by microtremor array measurements in Tekirdag region, NW Turkey

In this study, we aimed to explore the S-wave velocity structure of shallow soils using microtremors in order to estimate site responses in Tekirdag and surrounding areas (NW Turkey). We collected microtremor array data at 44 sites in Tekirdag, Marmara Ereglisi, Corlu, and Muratli. The phase velocities of Rayleigh waves were estimated from the microtremor data using a Spatial Autocorrelation method. Then, we applied a hybrid genetic simulated annealing algorithm to obtain a 1D S-wave velocity structure at each site. Comparison between the horizontal-to-vertical ratio of microtremors and computed ellipticities of the fundamental mode Rayleigh waves showed good agreement with validation models. The depth of the engineering bedrock changed from 20 to 50 m in the Tekirdag city center and along the coastline with a velocity range of 700-930 m/s, and it ranged between 10 and 65 m in Marmara Ereglisi. The average S-wave velocity of the engineering bedrock was 780 m/s in the region. We obtained average S-wave velocities in the upper 30 m to compare site amplifications. Empirical relationships between the AVs30, the site amplifications, and also average topographic slopes were established for use in future site effects microzonation studies in the region

A Physics-based Monte Carlo Earthquake Disaster Simulation Accounting for Uncertainty in Building Structure Parameters

AbstractPhysics-based earthquake disaster simulations are expected to contribute to high-precision earthquake disaster prediction; however, such models are computationally expensive and the results typically contain significant uncertainties. Here we describe Monte Carlo simulations where 10,000 calculations were carried out with stochastically varied building structure parameters to model 3,038 buildings. We obtain the spatial distribution of the damage caused for each set of parameters, and analyze these data statistically to predict the extent of damage to buildings