Fig. 2

This map of NW Alborz region shows IRSC stations (light gray triangular) and IIEES stations (dark gray triangular). White circles indicate all 1155 earthquakes reported in the period 2006–2010 and gray circles show the 750 earthquakes selected (to read the selection criteria, see the text) for local tomography; gray stars Sahand and Sabalan volcanoes, thin black lines main faults in the region, North Tabriz Fault (NTF). Horizontal node (crosses) spacing for the 3D model is 25 km. Red box shows the inversion cell size. White polygon illustrates the border of volcanic rocks around Sahand volcano based on the geology map (Haghipur and Aghanabati 1985). Red ellipse shows possible cluster of explosions. Fault plane solutions of large events (Mw >5.0) are from the global CMT catalogue (http://www.globalcmt.org/)