Seismotectonic investigation of the Alborz Mountains, Northern Iran, by means of an innovative algorithm for seismic moment tensor retrieval

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A complex and not well understood system of strike-slip and thrust faults accommodates NNE-SSW oriented shortening in the Alborz Mountains of northern Iran. To date, a heterogeneous, spatially disparate seismic network and a lack of appropriate methods have prevented detailed moment tensor studies in this region. Seismic moment tensors provide a general description of the physical processes and the magnitude of earthquakes. Their knowledge is therefore fundamental for seismotectonic and seismic hazard assessment studies. The feasibility of moment tensor retrieval is controlled by several conditions, limiting the available observations in many earthquake source studies worldwide. To overcome this, we will develop a timely and conceptually innovative algorithm to combine waveform data of broadband stations, as well as first motion body-wave polarities and probably also amplitude ratios of P- and S-waves of short-period stations and accelerometers. We will retrieve a new and representative number of seismic moment tensors in the Alborz Mountains and use them for seismotectonic interpretation. Our work will thus help extend the structural and geomorphic data base for seismotectonic interpretation and seismic hazard analysis in this crucial area of the Arabia-Eurasia collision zone. Beyond these advantages concerning regional seismotectonic aspects, the methodology developed in this project can also be applied to other tectonically active regions worldwide.