Spatial variations in the frequency-magnitude distribution of earthquakes at Mount Pinatubo volcano
Bulletin of the Seismological Society of America
By: J.J. Sanchez, S.R. McNutt, J.A. Power, and M. Wyss
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Abstract
The frequency-magnitude distribution of earthquakes measured by the b-value is mapped in two and three dimensions at Mount Pinatubo, Philippines, to a depth of 14 km below the summit. We analyzed 1406 well-located earthquakes with magnitudes MD ???0.73, recorded from late June through August 1991, using the maximum likelihood method. We found that b-values are higher than normal (b = 1.0) and range between b = 1.0 and b = 1.8. The computed b-values are lower in the areas adjacent to and west-southwest of the vent, whereas two prominent regions of anomalously high b-values (b ??? 1.7) are resolved, one located 2 km northeast of the vent between 0 and 4 km depth and a second located 5 km southeast of the vent below 8 km depth. The statistical differences between selected regions of low and high b-values are established at the 99% confidence level. The high b-value anomalies are spatially well correlated with low-velocity anomalies derived from earlier P-wave travel-time tomography studies. Our dataset was not suitable for analyzing changes in b-values as a function of time. We infer that the high b-value anomalies around Mount Pinatubo are regions of increased crack density, and/or high pore pressure, related to the presence of nearby magma bodies.
Suggested Citation
Sanchez, J., McNutt, S., Power, J., and Wyss, M., 2004, Spatial variations in the frequency-magnitude distribution of earthquakes at Mount Pinatubo volcano: Bulletin of the Seismological Society of America, v. 94, no. 2, p. 430-438, https://doi.org/10.1785/0120020244.
ISSN: 1943-3573 (online)
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Spatial variations in the frequency-magnitude distribution of earthquakes at Mount Pinatubo volcano |
| Series title | Bulletin of the Seismological Society of America |
| DOI | 10.1785/0120020244 |
| Volume | 94 |
| Issue | 2 |
| Year Published | 2004 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Bulletin of the Seismological Society of America |
| First page | 430 |
| Last page | 438 |