Influence of site conditions on near-source high-frequency ground motion: case studies from earthquakes in Imperial Valley, CA. , Coalinga, CA. , and Miramichi, Canada

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6289658

Mueller, C S

In this thesis, three recent earthquake datasets are analyzed in which local recording-site geology strongly modifies near-source ground motion in the 1-30 Hz band. Site effects in this frequency band complicate seismic-source observations, such as estimation of earthquake source parameters and high-frequency discrimination between earthquakes and explosions, and seismic-hazard predictions for components of large engineering systems. The goals of this work are to examine the details of site amplification, and, in the process, to assess how site effects might be quantified and incorporated into seismology and engineering practice. The Imperial Valley study is motivated by a remarkable 1.7 g peak vertical-component acceleration recorded at station 6 of the El Centro accelerograph array during the 15 October 1979 Imperial Valley, Ca., earthquake. Analysis of geotechnical data suggests a plausible amplification mechanism: P-wave resonance related to water saturation in shallow sediments at station 6. The Coalinga dataset consists of seismograms from 26 aftershocks of the 2 May 1983 Coalinga, Ca., earthquake. Average horizontal-component ground motion is amplified on alluvium at downtown Coalinga relative to nearby rock by a factor of 3-4 at frequencies up to 5-15 Hz. Amplification apparently trades off with attenuation on alluvium at high frequencies. The Miramichi dataset consists of seismograms from 40 aftershocks of the 9 January 1982 Miramichi, New Brunswick, Canada, earthquake. Source-parameter measurements are influenced by strong site effects at frequencies greater than 15Hz, due to resonance in shallow layers of glacial till over bedrock.

• Research Organization: Stanford Univ., CA (USA)
• OSTI ID: 6289658
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
ALLUVIAL DEPOSITS
AMPLIFICATION
CALIFORNIA
CANADA
CORRELATIONS
EARTHQUAKES
FEDERAL REGION IX
GEOLOGIC DEPOSITS
GEOLOGY
GROUND MOTION
MOTION
NORTH AMERICA
RESONANCE
SATURATION
SEISMIC EVENTS
SEISMIC P WAVES
SEISMIC WAVES
SITE SURVEYS
USA
WATER SATURATION
WAVE PROPAGATION