Abstract: Geological faults comprise large-scale segmentation and small-scale roughness that govern earthquake processes and associated seismic radiation. Recent large earthquakes demonstrate that standard techniques for seismic hazard assessment for such faults (fault systems) are insufficient. This problem can be overcome by numerical simulations for multi-scale geometrical complex faults to investigate their rupture dynamics and seismic radiation. In this presentation, I discuss recent work to understand effects of large-scale segmentation and small-scale roughness on rupture evolution and near-source shaking. Using numerical simulations, we find that rupture incoherence due to fault roughness leads to high-frequency spectral decay consistent with observations. Waveform characteristics and comparisons with empirical ground-motion relations show that rough-fault rupture simulations generate realistic synthetic seismogram that can be used for engineering applications. We also show that for segmented faults, the spatial distribution of the regional stress is of critical importance as it determines the initial stress on the fault system. Similarly, the rupture nucleation point has significant impact on the resulting rupture process and earthquake size. Consequently, seismic hazard assessment for such fault systems must include more earthquake physics to capture the possible near-source shaking levels of future earthquakes.

Bio: Prof. P. Martin Mai is professor in the Physical Sciences and Engineering Division at KAUST. He joined KAUST in June 2009 as founding faculty member. Prior to his affiliation with KAUST, Prof. Mai worked as senior research scientist at ETH Zurich, Switzerland. Since 2003, Prof. Mai has supervised more then twenty PhD and MSc students, guided ten postdoctoral researchers, and served on numerous student evaluation committees. Prof. Mai is an active member of the American Geophysical Union (AGU), the Seismological Society of America (SSA), the European Geosciences Union (EGU), and the German Geophysical Society (DGG). Prof. Mai has published over 90 peer-reviewed papers in highly ranked international journals, has (co-)organized several international workshops and conferences, and chaired many special sessions at international conferences. In 2015, he was elected Division President of the Seismology Division of the European Geosciences Union (EGU). At KAUST, he serves also as the Chair of the Earth Science Faculty (since July 2017) and as Associate Dean for the Division of Physical Sciences and Engineering (since Sept 2018).​

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