Event

The Faculty of Engineering will host a seminar entitled “A priori Forecasting of the strongest 1997 Earthquake near Tobago using b-value analysis and other ex post facto indicators”. The seminar will take place on Tuesday 17^th March 2009, in the Faculty Board Room, Block 1, Faculty of Engineering at 2:00 p.m. Joan Latchman, PhD. Student in Seismology, Department of Civil and Environmental Engineering, will present the seminar.

For further information, please contact the Department of Engineering at (868) 662-2002 Ext. 2065.  

Abstract: 

An earthquake of duration magnitude, Mt, 6.1 occurred on 1997/04/22 at 09:31 UTC just south-east of Tobago, an island in the Eastern Caribbean.  In the earthquake, some houses collapsed with 2 people requiring hospitalisation.  Some engineered structures suffered significant damage.  Locally, some springs ceased or increased their flow.  This event was the climax of a series of over 500 events Mt ³ 2.0, which had started on 1997/04/02 at 06:14 UTC with the occurrence of an Mt = 5.6 event north-west of Tobago.  As the series progressed, temporal plots of log N  vs M of a variant of the Gutenberg-Richter relation, log N = a - bM, were produced.  Based on the expectation that once the activity had run its course a near-straight line fit would be obtained, as happened in the 1982 Tobago sequence, it was deduced that the departures from linearity in the plot would become aligned with the occurrence of further large events, and at least one event larger than Mt = 5.6, within specific magnitude ranges.  The series had been in progress for thirteen days when, on 1997/04/15, it was postulated that the activity, up to that time, was still precursory, and not a simple decay sequence from the event of 1997/04/02.  On the basis of the temporal magnitude-frequency analysis it was projected that an event of magnitude at least 6.0 would occur.  Such an event did occur seven days later, on 1997/04/22.  Post-activity analysis revealed that the earthquakes belonged to two separate sequences.  Applying the techniques of pattern recognition and seismic gap analysis to the strongest events near Tobago since 1958 suggests that the next strong earthquake might be within a radius of about 30 km.