SOPAC Preliminary Report 135
Dr G. G. Shorten, SOPAC
On Thursday 3rd January 2002, a magnitude Mw 7.1 earthquake, the largest recorded so far in the vicinity, struck Port Vila (Figure 1). Although a significant event, it was by no means the largest possible in this setting. Estimates of maximum possible seismicity sit around magnitude 7.8.
The shock occurred at 04:22 am local time (UTC 2002/01/02 17:22:50), only 50 km to the west of Port Vila and at the shallow depth of 21 km below the sea floor. Fifteen minutes after the main shock, a tsunami (Figure 2) struck Port Vila Harbour. The event was followed that same night by another large aftershock of magnitude Mw 6.4 which also produced a tsunami, though much smaller.
The following day, the Director of SOPAC made a plea for international coordination of scientific and engineering assessments, and volunteered SOPAC as the reference point for information on the event. A SOPAC assessment team was readied and dispatched to Port Vila on Tuesday 8th January, and will remain there until 24th January, to obtain details of damage. The team has already consulted widely in Vanuatu: A list of persons and organisations with which meetings, discussions and inspections were held between 8th-13th of January is appended.
The UK Department For International Development (DFID) Suva responded rapidly and favourably to an approach and request from SOPAC, providing the much-needed funding for the assessment to take place.
Damage to the city and to southeast Efate in general was surprisingly light, although several bridges were destroyed and much cracking in concrete structures and superficial damage was recorded (Figure 3). The tsunami that struck Port Vila Harbour some 15 minutes after the first shock, was fortunately small enough, given the low tide at the time, not to cause any significant flooding above Highest Astronomical Tide level.
The majority of buildings fared well in the earthquake, and the most of the damage appears to be the result of either ground failure or inadequate structural design. Although the full extent of damage is still being assessed, earthquake damage currently falls into several categories:
- Significant structural damage
- Superficial building damage
- Foundation failure
- Slope failure
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