Analysis of Digital Teleseismic Array Data Collected in South Central Siberia and Northern Mongolia, GSN SKS Waves and S Waves from Lop Nor Nuclear Explosions
Abstract
Analysis of data we collected in south central Siberia and Northern Mongolia along with digital data from the Global Seismic Network have been analyzed to identify effects on propagation of large scale heterogeneity in the mantle that need to be taken into account when using seismic arrays to monitor the Comprehensive Test Ban Treaty. We find that in the vicinity of the Baikal rift zone in Siberia, P and S waves exhibit anomalous delays and attenuation. S waves show clear evidence of anisotropy effects. This anomalous region that extends over several hundred km either side of the rift zone, and is presumed to extend along the 600 km of its axis, represents an attenuating and delaying mantle barrier to seismic phases. These findings can be used to infer properties of analogous tectonic regions world-wide (Basin and Range of North America, Northern Tibet, East African and Rio Grande rifts, Red Sea, Gulf of California). We have analyzed all stations of the Global Seismic Network (GSN) for SKS splitting in the mantle. We compare SKS waveforms with normal mode synthetics modified by splitting by one or two layers of anisotropy in the mantle. Splitting is recognized as scattering of radial energy into tangential energy. We find that stations can be characterized by a single layer of splitting in their vicinity but for some arrivals scattering deeper in the mantle either due to a second layer of anisotropy or 3D scatterers gives anomalous tangential energy. This observation has led to development of a new method to identify deep mantle scatterers, by arrivals with anomalous tangential energy. We have examined P-S scattering from 12 Lop Nor nuclear explosions recorded at GSN stations in Asia. We have identified PcS and possible source generated S. Both show splitting effects that must be deconvolved before they can be confidently be interpreted as nuclear explosion P-S scattering.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 02, 2001
- Accession Number
- ADA387361
Entities
People
- Laura Borton
- Paul M. Davis
- Shangxing Gao
Organizations
- University of California, Los Angeles