Ocean Acoustic Analysis of the 1994 Northridge Earthquake
Abstract
Ocean acoustic activity was analyzed before and after the 1994 Northridge earthquake. Hydrophones in the California Continental Borderland recorded primary waves (P-wave) and tertiary waves (T-wave) over an 80-hour period. Ocean-based acoustic data was analyzed and compared to concurrent land-based seismographic data. The P-waves detected correlated with the land seismic events. The T-waves detected did not correlate with seismic data. T-waves, localized by Line of Bearing (LOB) cross-fixing, were along the Ferrelo Fault zone in a major lateral offset. Land seismic sensors showed no precursors to the earthquake. Ocean acoustic sensors showed seaquakes occurring at a rate of 5.3/hour, which stopped 31 hours 20 minutes prior to the main earthquake and returned to near prior activity levels 16 hours later. Ocean quakes may indicate energy release during earth movement and its absence indicates energy accumulation as elastic strain in rocks. Hydrophones provide a valuable means to monitor geologic activity in borderland regions and can contribute to the understanding of coastal earthquakes.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2023
- Accession Number
- AD1190148
Entities
People
- Ronald Wroblewski
- Scott C. Mcgirr
- Wayne L. Teeter
Organizations
- Naval Information Warfare Center Pacific