Passive seismic experiments (IU, UCSD, Rice)

Since submitting our original NSF proposal for this project the Venezuelan government deployed a new 33 station satellite-telemetered broadband national network, operated by FUNVISIS. The archival system that FUNVISIS used, however, only retained event segments for local earthquakes. To allow us to acquire teleseismic data from this network we placed a Sun computer at FUNVISIS headquarters in Caracas in 2003, and leased an internet circuit to transmit the continuous data from the FUNVISIS network to the U.S. in near real time. We intend to continue this data transfer and are working with FUNVISIS on an agreement to make these data available to the entire scientific community. Funding is requested in this proposal to maintain this link. To complement the 33 station FUNVISIS broadband array, we installed 27 PASSCAL broadband seismographs in Venezuela and deployed 15 OBSIP broadband seismographs in the southern Caribbean. The PASSCAL instruments were in place ~18 months (November 2003-May 2005), the OBSIP instruments 12 months (February 2004-February 2005), the maximum possible time given current OBS power sources. Thirteen of the OBSIP instruments returned data. Additionally, from November 2004 to the present we have operated 8 Rice owned broadband seismographs in Venezuela, 6 along active source profile 67W, and one each on Aruba and Curaçao. At the peak deployment, with FUNVISIS, PASSCAL, OBSIP, and Rice instruments, we were recording data on more than 80 broadband seismograph stations. The Rice instruments will be moved to profile 70W in March 2006 for approximately one year’s deployment, in conjunction with ~12 FUNVISIS portable instruments using residual funds from the original proposal to investigate this crucial area.

In May 2005, Pavlis reached an agreement for data exchange with the University of the West Indies Seismic Research Unit (http://www.uwiseismic.com) following a turnover in SRU leadership. UWI–SRU operates stations throughout the eastern Caribbean with two broadband stations on Trinidad and one broadband in each of their island networks. Of particular importance are broadband stations they operate on Trinidad, Grenada, and Barbados that provide coverage in our study area. In October 2005 we obtained all their data from December 2003 through May 2005. These are all event segmented data and contain only local events and teleseismic P waves. They will be useful for P wave tomography, seismicity studies, and receiver function studies proposed here. Their data is in a unique format and we are in the process of developing specialized code to allow us to utilize these data in our analysis. At present we have a reviewed catalogue for 192 days from 2003 through day 143 of 2004. During this period the arrays recorded 218 teleseisms and 565 regional and local events, or about 1 teleseismic and 2.5 local and regional events/day. Construction of the reviewed catalog is continuing.

Teleseismic, regional and local seismicity from BOLIVAR earthquake
catalogue for 192 days, roughly 35% of the data we have recorded.