Modeling Regional Seismic Waves
Abstract
This study can be divided into three main topics: modeling regional broad-band seismograms from the Imperial Valley to Pasadena, Determining surface wave magnitudes for NTS events using regional data, and waveform modeling to determine depth of earthquakes in Tibet leading to new origin times and a better estimation of P sub n and S sub n velocities. In section 1, broad-band wave propagation along a corridor from Imperial Valley to Pasadena, California is addressed. The path consists of 50 km of slow basin structure with a shallow moho followed by 250 km of relatively normal Southern California structure approaching Pasadena. In section 2, surface wave magnitudes for 112 Nevada Test Site (NTS) explosions from a data set of regional long-period seismograms from North American stations are calculated. In order to utilize the newer regional stations (Delta < 25 deg), a new method for determining M sub s has been developed which employs synthetic seismograms to establish a relationship between the amplitude of the regional Airy phase, or Rayleigh pulse, of the data and an associated surface wave magnitude, based on conventional M sub s determinations, calculated from a synthetic seismogram propagated to 40 deg. In section 3, a note on the relocation of the Tibetan earthquake is presented. Present ISC locations for earthquakes beneath Tibet indicates a random distribution of events down to a depth of about 50 km. A detained investigation of the Tibetan earthquakes, with magnitudes greater than 5.5 from 1964 to 1986, yields a distinctly different picture.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 31, 1991
- Accession Number
- ADA246894
Entities
People
- David G. Harkrider
- Donald V. Helmberger
Organizations
- California Institute of Technology