Timing of paleoearthquakes on the northern Hayward Fault: Preliminary evidence in El Cerrito, California

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 However, a recent study of historical documents concludes that the 1836 earthquake did not occur on the northern Hayward fault, thereby extending the elapsed time to at least 220 yr ago, the beginning of the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 ~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. Analysis was aided by rapid C-14 dating of more than 90 samples which gave near real-time results with the trenches still open. A combination of upward fault terminations, disrupted strata, and discordant angular relations indicates at least four, and possibly seven or more, surface faulting earthquakes occurred during a 1630-2130 yr interval. Hence, average recurrence time could be <270 yr, but is no more than 710 yr. The most recent earthquake (MRE) occurred after AD 1640. Preliminary analysis of calibrated dates supports the assumption that no large historical (post-1776) earthquakes have ruptured the surface here, but the youngest dates need more corroboration. Analyses of pollen for presence of non-native species help to constrain the time of the MRE. 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.

Arrest and recovery of frictional creep on the southern Hayward fault triggered by the 1989 Loma Prieta, California, earthquake and implications for future earthquakes

“… Lienkaemper et al [2001] shows that the southern Hayward fault has accommodated four large earthquakes with an average recurrence time of ∼140 years, with the most recent rupture occurring in 1868 with a M6.8 earthquake. Compiled paleoseismic data on the three recent earthquakes on the northern section of the fault by the Hayward Fault Paleoearthquake Group indicate an average recurrence time of ∼210 years [ Lienkaemper et al , 1999]. The Working Group on California Earthquake Probabilities [2003] suggests that the Hayward possesses a 27% probability of generating a 6.7 or more magnitude earthquake within the next 30 years.…”

Marine Paleoseismic Evidence for Seismic and Aseismic Slip Along the Hayward‐Rodgers Creek Fault System in Northern San Pablo Bay

“…Here we present a multi-disciplinary approach to conducting on-fault marine paleoseismologyand present evidence for both vertical aseismic creep and coseismic (Waldhauser & Schaff, 2021); green stars, existing paleoseismic trench sites discussed in this paper. MH, Masonic Home (Lienkaemper & Borchardt, 1996); MV, Mira Vista (Lienkaemper et al, 1999); SP, San Pablo (this study); TG, Triangle G (Hecker et al, 2005); TL, Tyson's Lagoon (Lienkaemper et al, 2002). AR, Alum Rock; H, Healdsburg; L, Livermore; O, Oakland; SE, Sears Point; SF, San Francisco; SR, Santa Rosa.…”

“…Black lines, U.S. National Seismic Hazard Model 2023 fault sections (modified from Hatem et al, 2021); thick purple bars, fault section boundaries (modified from Field et al, 2013); blue circles, locations of repeating earthquakes that are interpreted to indicate the presence of creep at depth(Waldhauser & Schaff, 2021); green stars, existing paleoseismic trench sites discussed in this paper. MH, Masonic Home(Lienkaemper & Borchardt, 1996); MV, Mira Vista(Lienkaemper et al, 1999); SP, San Pablo (this study); TG, Triangle G(Hecker et al, 2005); TL, Tyson's Lagoon(Lienkaemper et al, 2002). AR, Alum Rock; H, Healdsburg; L, Livermore; O, Oakland; SE, Sears Point; SF, San Francisco; SR, Santa Rosa.…”

“…Figure 10. Plot showing the estimated timing of past surface-rupturing earthquakes from onshore (Hecker et al, 2005;Lienkaemper et al, 1999Lienkaemper et al, , 2002Schwartz et al, 1992) and offshore (this study) paleoseismic investigations along different sections of the Hayward-Rodgers Creek fault (see Table 5 for more details). See Figure 1 for locations of fault section boundaries and paleoseismic sites.…”

Probabilistic Estimates of Surface Coseismic Slip and Afterslip for Hayward Fault Earthquakes

“…Paleoseismic studies of the Hayward fault, for example, Lienkaemper et al (1999), Lienkaemper et al (2002, and Lienkaemper and Williams (2007), do not provide estimates of the slip per event to which we can compare our coseismic slip estimates. Nevertheless, the scarp colluvium features and fissure fills used by Lienkaemper et al (2002) and Lienkaemper and Williams (2007) to identify 12 earthquakes at Tyson's Lagoon in the past 1900 years appear to be consistent with formation by coseismic slip.…”