Moment Magnitude (Mw):
Greenwich Mean Date:
SANTA CRUZ / VANUATU ISLANDS REGION
A moderate aftershock sequence has followed yesterday's powerful earthquake in the Santa Cruz Islands. Although numerous M3s and M4s have been recorded, only five events have measured M5 or stronger. The largest was the M6.1 which occurred about 9 minutes after the main jolt (Seismo-Watch Earthquake Alert Bulletin 97-094). Of the other four M5+ aftershocks, the above event has been the largest thus far.
The National Earthquake Information Center has determined a Moment magnitude of Mw 7.5 for the Santa Cruz Island earthquake. The focal depth was 26 km and the focal mechanism was nearly pure thrust motion along a shallow northwest orientation, compatible with the Northern Hebrides subduction zone. Harvard Geophysical Laboratory determined a Moment magnitude of Mw 7.8 but their focal depth was calculated at 37 km deep. Maximum vertical displacement is probably on the order of 2-3 meters, thus creating a new shoreline for some of the islands near the epicenter.
Wire reports for this event have been unusually absent. There have been no reports of tsunamis nor of damage or injuries as of yet.