Interaction between shallow and subcrustal dislocations on a normal fault |
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| Institution: | 1. College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China;2. College of Public Administration, Zhejiang University of Finance & Economics, Hangzhou 310018, China;3. The Architectural Design & Research Institute of Zhejiang University Co, LTD, Hangzhou 310028, China;1. Hacettepe University, Department of Geological Engineering, Hydrogeology Division, Beytepe, 06800 Ankara, Turkey;2. Institute of Earth Sciences, Academia Sinica, Taiwan;3. Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Via Ugo La Malfa, 153, 90146 Palermo, Italy;4. Department of Geosciences, National Taiwan University, Taipei, Taiwan;5. National Center for Research on Earthquake Engineering, NARL, Taiwan;1. Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 3173-25 Showa-machi, Kanazawa-ku, Yokohama, Kanagawa 2360001, Japan;2. Kandilli Observatory and Earthquake Research Institute, Bogazici University, 34686 Cengelkoy-Istanbul, Turkey;3. Institute of Education, Research and Regional Cooperation for Crisis Management Shikoku, Kagawa University, 2217-20, Hayashi-cho, Takamatsu 7610396, Japan;1. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi''an, China;2. Department of Geophysics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan |
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| Abstract: | We propose a model which may explain seismic sequences which are often observed in seismogenic regions, as for example in the Apenninic chain (Italy). In particular, we consider a normal fault and earthquakes taking place at different depths: a first shock in a shallower layer and a second in a deeper one. The normal fault is embedded in a viscoelastic half-space. As a consequence of the rheology, there are two different brittle layers, a shallower and a deeper one, where earthquakes can nucleate. Between these two layers, the rheological behavior is ductile. The thicknesses of the layers depend on the geothermal profile that is calculated taking into account the profile of the thermal and rheological parameters with depth. The fault plane, crossing layers with different rheological behavior, is heterogeneous in respect to the slip style: seismic in the brittle layers, aseismic in the ductile layer. Dislocations in the shallower layer are assumed to produce aseismic slip in the area of the fault belonging to the ductile layer. The stress concentrated, by the seismic and aseismic dislocations, on the fault plane section in the deeper brittle layer is evaluated. It is compared with the tectonic stress rate in order to calculate how much earlier the second earthquake would occur compared to if just the bare tectonic sstress was acting. It results that such an advance is comparable with typical recurrence times of earthquakes and so a mechanism of interaction between different seismic sources, mediated by aseismic slip, can be supposed. The strains and displacements at the Earth’s surface due to seismic and aseismic slip are calculated. They are large enough to be detected by present geodetic techniques. |
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