A comparison between seismicity, topographic relief, and gravity anomalies of the Iranian Plateau

Abstract

Both theoretical treatment and observed data have demonstrated that the stresses induced by topography are appreciable and may cause seismicity to concentrate in regions of large topographic and/or gravity anomalies corresponding to isostatic anomalies. Their magnitudes range from a few to hundreds of MPa. Data on seismicity, topographic relief, isostatic and Bouguer anomalies of the Iranian Plateau were correlated with each other, using the bivariate statistical method. The results indicate that all of the parameters analyzed appear to show positive correlation with each other. Among the parameters studied, the topographic setting and the isostatic anomaly exhibit more significant relationships with the earthquake activity in the region. Therefore locations of large topographic relief and/or isostatic anomalies, where strong earthquakes have not occurred in historic times, should be considered as potentially hazardous zones where future strong earthquakes may take place. The results further suggest that there is a connection between the Bouguer anomalies and the occurrence of small (or local) earthquakes. The results also denote that the topographic relief, the isostatic anomalies and the Bouguer anomalies have relatively high correlations with each other, except for the regional Bouguer anomaly which appears to have low correlation with the topographic relief. These factors should be considered in the studies of earthquake activity, seismic zoning, and hazard estimation of tectonically active regions.