Surface-wave Tomography of East African Rift System using Ambient Seismic Noise
Abstract
The surface-wave tomography technique for the ambient seismic noise is applied to the east African rift system to investigate shallow crustal structures of the region. Even if the technique has been widely used in many regions to investigate crustal structure in the world, there have been difficulties in application of the technique to the east African region because of unstable data conditions of PASSCAL experiments. A meticulous check of record by record enables us of applying the technique to understand the tectonic environment of the region. The long-period data of one month showing good quality in cross-correlation results are used in this study. They are from the 1994-95 Tanzania Passive-Source Seismic Experiment for the Tanzania craton and its surrounding rift zone, and from the 2000-02 Ethiopia/Kenya Broadband Seismic Experiment and the adjacent permanent stations of the African Array for the Ethiopia rift. The Rayleigh- and Love-wave group-speed maps were inverted using LSQR algorithm for several period bands (5 - 50 s). The preliminary group-speed distribution maps yield results roughly consistent with regional geology. The tomographic images of the Tanzania region show a strong high velocity anomaly at the location corresponding to the Tanzania craton and low velocity anomalies at the surrounding rift regions. For the Ethiopia regions, the features of low velocity anomalies roughly agree with the Tertiary volcanic regions. Combining the Tanzania and Ethiopia broadband arrays, the outline of the east African rift system can be identified as the low velocity anomalies in the surface-wave tomographic results. The structural variation with depth and the feature of the regional shear-wave anisotropy of crust will be explored by converting group- speed dispersion curves into shear-wave velocity structure.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.S31A1879K
- Keywords:
-
- 1207 Transient deformation (6924;
- 7230;
- 7240);
- 1219 Gravity anomalies and Earth structure (0920;
- 7205;
- 7240);
- 7255 Surface waves and free oscillations;
- 7270 Tomography (6982;
- 8180)