TOMODEC. High resolution seismic tomography of Deception Island (Antarctica), and modelling of seismo-volcanic sources

Brief description

The TOMO-DEC experiment was organized in three main legs: (1) a search for sites to deploy seismic stations and for temporary camps to accommodate the researchers (austral summer 2003-2004); (2) the field phase of data collection during the austral summer 2004-2005; and finally (3) a laboratory phase of data gathering, organization and analysis, that still ongoing as papers continue to be published. The preliminary analysis of data involved an initial phase of data gathering from instruments of different types, their organization in a joint database, their conversion to a common format and, finally, the determination of the first P-wave arrival times.
Leg 1 was performed during two summer field expeditions (2002-2003 and 2003-2004). The whole island was surveyed (including glacial areas) in order to identify potential sites for seismic stations and camps.
Leg 2 took place between December 2004 and March 2005 with most of the activity focused in the deployment of seismic stations (on land and OBSs), air-gun shooting, data collection and final recovery of the majority of the seismic stations. This experiment took place between January 4 and January 24, 2005.
Ninety-five on-land seismic stations and 14 OBSs were deployed. They included 7 Lennartz Marslite seismic stations (covering 14 positions), four M24 instruments (covering 7 positions) and 11 seismic arrays (with 84 short period sensors, occupying a total of 101 different positions), all of them working in continuous recording mode. Active seismic sources were generated using an array of air-guns with a maximum capacity of 3520 cubic inches. Together with the seismic waveforms, a final dataset consisting of travel times for more than 70000 crustal P-wave first arrivals was collected. Bathymetric data were recorded using both EM120 and EM-1002 multi-beam sounders and a SIMRAD EA-600 single-beam sounder. Magnetic profiles were obtained using the MarineMagnetics SEASPY marine magnetometer on the base of an Overhauser sensor. Finally gravimetric data were acquired using the marine gravimeter BELL AEROSPACE-TEXTRON BGM-3. In total more than 1000 km of profiles were acquired with all types of data. The experiment at Deception Island was organized in collaboration with several research institutions. For the field work and data collection the following institutions (with number of researchers and provided instruments) participated: Instituto Andaluz De Geofisica, Spain (12, 10 land seismic arrays of malIAG type); Lamont Doherty Earth Observatory, Columbia University, USA (4, 14 OBS); INGV-Osservatorio Vesuviano, Italy (1, 7 land stations of Marslite type); INGV-Catania, Italy (1, 4 land stations of M24 type); CENAPRED, Mexico (1); Universidad De Cadiz, Spain (2); Universidad De Colima, Mexico (1); University College Dublin, Ireland (1); Universidad Complutense De Madrid, Spain (1); Universidad De La Plata, Argentina (1); University Of Washington, USA (3); USGS Volcanic Hazard Team, USA (2).

Lineage

Progress Code: completed

Statement: The quality of data registered during the seismic experiment was very good, with low noise recorded by both on-land and ocean bottom seismometers. Due to the nature of the emplacement site, cultural noise was completely absent. The record quality decreased on on-land stations during high winds, and in OBS records when the sea waves were high.

Notes

Purpose
In January 2005 a multi-parametric international experiment was conducted that encompassed both Deception Island and its surrounding waters. This experiment used as main platforms the Spanish Oceanographic vessel 'Hesperides', the Spanish Scientific Antarctic base 'Gabriel de Castilla' at Deception Island and four temporary camps deployed on the volcanic island. This experiment allowed us to record active seismic signals on a large network of seismic stations that were deployed both on land and on the seafloor. In addition other geophysical data were acquired, such as: bathymetric high precision multi-beam data, and gravimetric and magnetic profiles. The seismic and bathymetric data have been analyzed but the magnetic and gravimetric data have not. We provide P-wave arrival-time picks and the seismic tomography results in velocity and attenuation. The data set presented in this article has been analyzed following different approaches and techniques providing new and interesting results associated with the nature and structure of the island. Tomographic and structural images of velocity and attenuation have been used to help in the interpretation of the inner structure of the volcano, sometimes combined with bathymetric analysis.