Large Scale Simulation of Ground Motions for Heterogeneous Source Models By Fdm Reciprocity Method


Abstract eng:
For this study we used hierarchical heterogeneous source modeling procedure of Sekiguchi et al., 2008. This modelling approach is a result of compilation of many source observations (inversions) of strong earthquakes and allow easily generate possible variations of slip distributions. As a result, we can apply probabilistic approach to study generated ground motions. Namely, we can estimate effect of many heterogeneous source models that reproduce observed (inverted) slip patterns, and choose models that have average, average plus standard deviation, or certain probability of non-exceedance levels of strong ground motions (e.g. response spectra in period range of a target structure). Many models have to be calculated in this case. E.g., in order to estimate average plus standard deviation level we may need to calculate 30 models, and we will need 2-3 times more models, when need to choose specific source model that reproduce this level. We applied above methodology to study long-period ground motions in the Osaka sedimentary basin, Japan, from a hypothetical M9 earthquake in Nankai Trough, which has high probability of occurence within next 30 years. For computing long-period motions, we used detailed 3-D crust and basin velocity structure model JIVSM, developed for Japan. Simulation space is around 820km in EW direction, 550km in NS direction and 70km in depth, and shortest period to simulate is 3sec. It takes 3 days to calculate 300sec record by FDM. Because time consuming 3D-FDM method is used, in order to calculate many source models we employed reciprocity method. For this simulations, we constructed multiscale heterogeneous source models based on the characterized source model of the Central Disaster Management Council of Japan (CDMC, 2012) and simulated long-period ground motions in period range 3-20 sec using FDM. Natural periods of many high-rise buildings and other construction structures, e.g. numerous suspension bridges around Osaka bay, fall into this period range. 300 source models are generated randomly from initial characterized source model. Source parameters, which have randomly generated heterogeneities, are: slip, rupture velocity Vr and location of SMGAs. Moreover, in order to account for variations of directivity effect, we generated ground motions for three cases of rupture start: in center of model and in west and east sides of model. In the deepest landward part of Osaka basin (site Konohana, depth of sediments 1500m) the ground motions at larger NS component are estimated to have peak velocities of 40–80 cm/s, prolonged durations exceeding 300 s, and long predominant periods of 5–10 s, and velocity response spectra for this periods of 190 cm/s in average, or 290 cm/s for average plus standard deviation. Effects of rupture heterogeneity (slip and Vr), SMGA location and rupture starting point are approximately equal: about 30% of average amplitudes of ground motions. Variations of amplitudes among all 300 models are around 50%.

Contributors:
Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
Rights:
Text je chráněný podle autorského zákona č. 121/2000 Sb.



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 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 2932.:
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