Measurements of P and S wave fronts from the dense three-dimensional array at Garni, Armenia

Bulletin of the Seismological Society of America

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Abstract

The P- and S-wave arrivals from local earthquakes were studied using an array of 10 three-component instruments in and around a tunnel at Garni Observatory, Armenia. The array has a three-dimensional configuration with lateral dimensions of 300 to 500 m and a depth extent of 100 m. Estimates of the horizontal and vertical components of slowness for P and S wave fronts were used to determine the angles of approach and the propagation velocity. The results showed that the region around the array has low average velocities for both the P (1.43 km/sec) and S (0.61 km/sec) waves, so wave fronts approach the array at steep angles of incidence. Waveforms from one event show clear reflections from the free surface for both P and S waves. The timing of these reflections gives the velocity variation with depth within the array. We estimated a P velocity of 0.33 km/sec within a few meters of the surface, increasing to several kilometers per second for the deepest portion of the array. Local site variations can greatly complicate the high-frequency waveforms, even for tunnel stations in bedrock. The S waves exhibit stronger site dependent waveforms and time delays than do the Pwaves.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Measurements of P and S wave fronts from the dense three-dimensional array at Garni, Armenia
Series title Bulletin of the Seismological Society of America
Volume 84
Issue 4
Year Published 1994
Language English
Publisher Seismological Society of America
Description 8 p.
First page 1089
Last page 1096