Abstract

• Title
• Abstract
• Chapter 1
• Chapter 2
• Chapter 3
• Chapter 4
• Chapter 5
• Chapter 6
• Figures
• Chapter 1
• Chapter 2
• Chapter 3
• Chapter 4
• Chapter 5
• Chapter 6

The study of seismicity associated with identified seismic gaps is one tool which can be used for developing earthquake prediction methodologies. The Anza seismic slip gap along the San Jacinto fault zone in southern California is thought to be one of the most likely locations for a magnitude 6 or greater earthquake in the state of California. This gap is also known to be seismically active for magnitudes smaller than 5.0 and is entirely situated in the Peninsular Ranges batholith.

In this study we installed the ANZA seismic network in the region of the Anza seismic slip gap to record local earthquakes with a magnitude range of M_L = 1 - 4. This network was installed specifically to examine the scaling laws of body-wave spectra, the character of high frequency ground motion, and the physical interpretation of seismic stress drops. The network consists of 10 high dynamic range three-component stations, telemetered to La Jolla, California, and has recorded 2239 events between network startup and February 18, 1989. Source parameters estimated from P and S waves encompass a range of scalar seismic moment from 10¹⁰ to 10¹⁵ N-m and a distribution of estimated stress drops from 0.1 to 200 bars. The source parameters have standard deviations which range from 40% to 140% of the mean value. Measurements made from 300 meter deep borehole sensors and a small aperture seismic array are used to determine possible causes for the large standard deviations.

The possible benefits of using multiple taper spectral analysis are investigated. The multiple taper techniques are extended to estimate the coherence between seismic waveforms and to calculate the polarization, as a function of frequency, for seismic arrivals at a 3-component station. These techniques provide more stable estimates than the conventional single taper methods.

The application of the sophisticated data acquisition and analysis techniques indicate that the surface weathering layers can affect the estimation of the seismic source spectrum. To improve future measurements will require the use of more borehole sensors.