NEHRP Clearinghouse
- Title
- Timing of Paleoearthquakes on the Northern Hayward Fault: Preliminary Evidence in El Cerrito, California.
- File
- PB2006108457.pdf
- Author(s)
- Lienkaemper, J. J.; Schwartz, D. P.; Kelson, K. I.; Lettis, W. R.; Simpson, G. D.
- Source
- January 1999, 40 p.
- Identifying Number(s)
- USGS-OFR-99-318
- Abstract
- The Working Group on California Earthquake Probabilities estimated that the northern Hayward fault had the highest probability (0.28) of producing a M7 Bay Area earthquake in 30 years (WGCEP, 1990). This probability was based, in part, on the assumption that the last large earthquake occurred on this segment in 1836. However, a recent study of historical documents concludes that the 1836 earthquake did not occur on the northern Hayward fault, thereby extending the elapsed time to at least 220 yr ago, the beginning of the written record. The average recurrence interval for a M7 on the northern Hayward is unknown. WGCEP (1990) assumed an interval of 167 years. The 1996 Working Group on Northern California Earthquake Potential estimated approx 210 yr, based on extrapolations from southern Hayward paleoseismological studies and a revised estimate of 1868 slip on the southern Hayward fault. To help constrain the timing of paleoearthquakes on the northern Hayward fault for the 1999 Bay Area probability update, we excavated two trenches that cross the fault and a sag pond on the Mira Vista golf course. As the site is on the second fairway, we were limited to less than ten days to document these trenches. The earthquake recurrence estimates described in this report are preliminary and should not be used as a basis for hazard estimates. Additional trenching is planned for this location to answer questions raised during the initial phase of trenching.
- Keywords
- ; Methodology; Faults (Geologic); Schematic diagrams; Open-file report; Paleo-earthquakes; Tables (Data); Paleoecology; El Cerrito (California); Paleoseismology; Hayward fault (California); Earthquakes