Hi All,

Well the first day was very interesting. We met with Roger Bilham of the University of Colorado and enjoyed his explanation of an old earthquake which upon real time study, brought the information to life.

On 12/31/1881 there was a 7.9 quake in the Bay of Bengal. The quake occurred on the eastern side of the sea and from securing data for a tsunami on the western side of the bay, they were able to locate the epicenter of this earthquake.

In visiting the area one of the markers for this event was a tidal gauge with a clock and the clock stopped at the time of the tsunami. In the other city north of this location, another clock stopped precisely at the same time.

While the abstract for this poster is listed below, both Don and I found this an interesting study which goes along with our interest in Paleoseismology. This is an area we will attend lectures on come Friday.

Tomorrow we have a very busy day ahead. A Seismotech luncheon, a series of lectures, after lecture receptions and a Planetary Sciences dinner at an Italian restaurant in the city. I am certain we will enjoy all of the days events.

Rupture Parameters of the 1881 Mw=7.9 Andaman Sea Earthquake Estimated from Tide-Gauge Recordings Surrounding the Bay of Bengal
AU: Ortiz, M
EM: ortiz@cisese.mex
AF: Dept.Oceanografica,CICESE, 107 Carr.Tijuana, Ensenada, 22860 Mexico
AU: * Bilham, R
EM: bilham@colorado.edu
AF: CIRES and Geol. Sci., Univ. of Colorado, Boulder, 80309-0399 United States
AB: On the morning of 31 December 1881 a tsunami with a maximum crest height of 0.8 m was recorded by eight tide gages surrounding the Bay of Bengal, and by astronomical clocks in Madras and Calcutta. Waveform and amplitude modeling of the tsunami indicate that it was generated by a Mw=7.9$\pm$0.2 earthquake with 2-3 m of reverse slip on a submarine rupture located east of the south Andaman and Nicobar Islands. The earthquake did not occur on the upper surface of the Indian Plate. Instead it ruptured a 200 km by 50 km reverse-fault bounded to the east by the West Andaman Fault and to the west by the crest of the Andaman/Nicobar ridge between 8.5 $^{\circ}$N and 10.5 $^{\circ}$N. The tsunami data are of sufficient quality to permit us to estimate that reverse slip on the northernmost segment of the rupture was roughly 50\% less than slip on the southern section, and that slip in an intervening region was minor. The renewal time for 1881-type events is estimated to be 100-150 years although the occurrence of great earthquakes on the upper surface of the Indian plate is likely to compete with the available convergence budget that drives these events. In that the earthquake precedes the world's first recording seismometer by 8 years, and the first global seismic network by many decades, we believe that this may be one of the first earthquakes in history whose rupture parameters and magnitude have been quantified teleseismically.

Eos. Trans. AGU. 82 (47).
Fall Meet.Suppl.Abstract XXXXX-XX.2001
(c) 2001 American Geophysical Union