Structural Interpretation and Precursory Analysis for Ahar-Varzaghan Earthquake Based on Comparative Study of Seismic and GPS data

One of the most common parameter in seismic studies is b-value that is proportional to the relative earthquake-size distribution. This parameter is actually the slope of the Gutenberg-Richter law and depends on tectonics and stress distribution in the region. In this study, we investigated spatial and temporal changes of b-value and its confirmity with GPS data before and after the Ahar-Varzaghan earthquake in the northwest seismotectonic region of Iran. The spatial and temporal changes of b-value were mapped using the Zmap software. The map of spatial changes of b-value show doublet events occurred in low b-value area which is probably structurally different from adjucent areas. The temporal changes of b-value also represent intense and abrupt decrease of b-value a few days before the earthquake. The time series of the GPS stations at low b-value area showed dramatic change for a while before the main shocks. Seismic and GPS data, together, could have been considered as earthquake precursors if they had been monitored precisely and continuously. Based on this calculation, the time series of GPS data and field observations, we proposed a restraining bend structure causing the earthquake. The proposed structural model can help to estimation seismic hazard risk of potential future failure area.