Rapid kinematic finite-fault inversion for an Mw 7+ scenario earthquake in the Marmara Sea: An uncertainty study

Abstract:

During the 20th century, a series of devastating earthquakes occurred along the North Anatolian Fault. These generally propagated westwards, such that the main fault segment beneath the Marmara Sea as a seismic gap. For the nearby megacity Istanbul, rapid seismic hazard assessment is currently of great importance. A key issue is how a strong earthquake in the Marmara Sea can be characterized reliably and rapidly using the seismic network currently operating in this region. In order to investigate this issue, a scenario earthquake on the main Marmara fault is simulated through dynamic modeling based on a 3D structure model. The synthetic datasets are then used to reconstruct the source processes of the causal events with a recently developed iterative deconvolution and stacking method based on simplified 1D earth structure models. The results indicate that, by using certain a-priori information about the fault geometry and focal mechanism, the tempo-spatial slip patterns of the input scenarios can be well resolved. If reasonable uncertainties are considered for the a-priori information, the key source parameters, such as moment magnitude, fault size and slip centroid, can still be estimated reliably, while the detailed tempo-spatial rupture pattern may reveal significant variations. To reduce the effect induced by employing the inaccurate event location and focal mechanism, a new approach for absolute source imaging is proposed and tested. We also investigate the performance of the new source imaging tool for near real-time source inversion under the current network configuration in the Marmara Sea region. The results obtained are meaningful particularly for developing the rapid earthquake response system for the megacity Istanbul.