Premonitory changes in seismic velocities, observations, causal mechanisms and application to earthquake prediction
Abstract
The nature and causes of certain phenomena precursory to earthquakes in an effort to develop a unified approach to the earthquake prediction problem was determined. The occurrence and recording of an earthquake swarm at Blue Mountain Lake, New York, in May-August 1971 provided an unusual opportunity to study earthquake processes at close range. The near total absence of sedimentary cover, accessibility of the epicentral area (2 x 2 km), the shallow focal depths, allowed excellent recordings of both P and S phases at short distances. Most of the events occurred on a well defined, easterly dipping thrust fault of relatively narrow thickness (0.2 km). The data revealed the occurrence of premonitory changes in the travel-time ratio of S to P waves, preceding all the larger events (mb = 2.5 to 3.3) in the swarm. Typically t sub s/t sub p at first decreased and subsequently returned to normal prior to the earthquake.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1975
- Bibcode:
- 1975PhDT........16A
- Keywords:
-
- Earthquakes;
- Seismic Waves;
- Lakes;
- New York;
- Seismology;
- Geophysics