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Located within a basin structure, at the conjunction of North East Anatolian, North Anatolian and Ovacik Faults, Erzincan city center (Turkey) is one of the most hazardous regions in the world. Combination of the seismotectonic and geological settings of the region has resulted in series of significant seismic activities including the 1939 (Ms~7.8) as well as the 1992 (Mw = 6.6) earthquakes. The devastative 1939 earthquake occurred in the pre-instrumental era in the region with no available local seismograms. Thus, a limited number of studies exist on that earthquake. However, the 1992 event, despite the sparse local network at that time, has been studied extensively. This study aims to simulate the 1939 Erzincan earthquake using available regional seismic and geological parameters. Despite several uncertainties involved, such an effort to quantitatively model the 1939 earthquake is promising, given the historical reports of extensive damage and fatalities in the area. The results of this study are expressed in terms of anticipated acceleration time histories at certain locations, spatial distribution of selected ground motion parameters and felt intensity maps in the region. Simulated motions are first compared against empirical ground motion prediction equations derived with both local and global datasets. Next, anticipated intensity maps of the 1939 earthquake are obtained using local correlations between peak ground motion parameters and felt intensity values. Comparisons of the estimated intensity distributions with the corresponding observed intensities indicate a reasonable modeling of the 1939 earthquake.
The Xiaojiang fault zone constitutes part of the major Xianshuihe¨CXiaojiang left lateral structure that bounds the rhombic-shaped block of Yunnan¨CSichuan to the east. Long strike slip fault zones that have repeatedly accommodated intense seismic activity, constitute a basic feature of southeast China. Known historical earthquakes to have struck the study area are the 1713 Xundian of M6.8, 1725 Wanshou mountain of M6.8, the 1733 Dongchuan of M7.8, and the strongest one, the 1833 Songming of M8.0. Although instrumental record did not report events of this magnitude class, the 18th century clustering as well as the 19th century large event prompted the investigation of stress transfer along this fault zone. Coulomb stress changes were calculated assuming that earthquakes can be modeled as static dislocations in an elastic half-space, and taking into account both the coseismic slip in strong (M ˇÝ 6.8) earthquakes and the slow tectonic stress buildup along the major fault segments. Geological and geodetic data are used to infer the geometry of these faults and long term slip rates on them, as well as for the fault segments that slipped. Evidence is presented that the strong historical events as well as the ones of smaller magnitude that occurred during the instrumental era, are located in areas where the static stress was enhanced. By extending the calculations up to present, possible sites for future strong events are identified.
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