with magnitudes estimated to be 6.5–7.0 based on macroseismic data. The countries surrounding the gulf have been actively monitoring the seismicity there since the 1980s and have found a consistent low level of activity, but a primary characteristic of the activity is that there are multiple sequences of earthquake swarms. Three swarm events, beginning in the north and ending in the south gulf, have been observed beginning in 1983 when more than 1,000 events occurred over a three-month period near the northeastern boundary of the Elat Deep (in the northern gulf) with the largest three events approaching 5 on the Richter magnitude scale. A less pronounced swarm occurred in 1990 with the largest event reaching 4.3 in the central gulf near the Elat Deep and the Arogonese Deep. The last significant swarm happened in 1993 in the southwestern Arogonese Deep (in the southern gulf) with the highest magnitude of 6.1 and more than 300 larger than magnitude 3 in the following weeks. Aftermath During several independent field studies cracks and other ground deformations were observed on both the Egyptian and Saudi Arabian sides of the gulf. During a field survey that was done there in 1996, a series of cracks were discovered between 28°35' N and 29°05' N on the Saudi Arabian coast. A field investigation was also done in Egypt in 1996 by seismologist Yann Klinger and others along with the Egyptian Geological Survey and Mining Authority. The most dramatic ground ruptures found were north of Nuweiba along a coastal road. The countries surrounding the gulf (Egypt, Israel, Jordan, and Saudi Arabia) operate their own seismic networks and during the months that followed the main event, fourteen temporary and permanent stations recorded thousands of aftershocks. Klinger acquired data on approximately 1,000 aftershocks via the European-Mediterranean Seismological Center and the agencies of each country. The data was filtered to include only those aftershocks within of the epicenter. Data from four stations from the Institute for Petroleum Research and Geophysics of Israel plus seven stations from Jordan's Natural Resource Authority recorded aftershocks in the epicentral area that met the restriction. It was found that the aftershocks were arranged with a north-south alignment over a length of and that was expected from an earthquake of such magnitude. The group of aftershocks were bunched in two distinct clusters, with one in the north and one further south. See also List of earthquakes in