The major seismic faults in Taiwan correspond to the various suture zones between the various terranes. These have produced major quakes throughout the history of the island. On 21 September 1999, a 7.3 quake known as the "921 earthquake" killed more than 2,400 people. The seismic hazard map for Taiwan by the USGS shows 9/10 of the island at the highest rating (most hazardous).