Modeling errors, bias and error regions in IMS seismic monitoring of Israel

The International Monitoring System (IMS) must meet the difficult challenge of monitoring global seismic activity with a sparse network to verify compliance with the comprehensive nuclear-test-ban treaty (CTBT). Data from the IMS will be processed by the International Data Center (IDC) to locate events and to screen out those that are clearly natural events. Accurate location of events is important because a suspicious event could lead to an on-site inspection that will focus on the region of the determined epicenter. We explore the question of potential IDC location errors for seismic events in Israel. We consider both systematic location bias due to inaccuracies in the travel time model and statistical variation due to errors in picking phase onsets. We find that systematic epicentral bias might be as large as 30 km, despite a relatively good station configuration, in which case it will dominate the statistical errors.