SCEC Award Number 13132 View PDF
Proposal Category Collaborative Proposal (Special Fault Study Area)
Proposal Title Determining Long-term Slip Behavior on the Mission Creek and Banning faults of the southern San Andreas Fault Zone: Geochronometry of Offset Landforms
Investigator(s)
Name Organization
Warren Sharp Berkeley Geochronology Center Kimberly Blisniuk Berkeley Geochronology Center Katherine Scharer United States Geological Survey
Other Participants
SCEC Priorities 1, 4 SCEC Groups SoSAFE, Geology
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 The potential for a large-magnitude earthquake (Mw ≥ 6.7) on the southern San Andreas fault zone (SAFZ) is generally considered high [Working Group on California Earthquake Probabilities, 2007]. However, the proportion of slip accommodated by each of its three major fault strands (Mission Creek, Banning, and Garnet Hill, from north to south) in the Indio Hills is poorly constrained. To better assess the relative importance of these faults and their potential for a major earthquake, we dated offsets on the Mission Creek and Banning faults in the central Indio Hills. Previous work in the southern Indio Hills on the Mission Creek fault strand at Biskra Palms, demonstrated a slip rate between 12 and 22 mm/yr, with a preferred rate of 14-17 mm/y. Northwest from Biskra Palms, it is generally assumed that the slip rate on the Mission Creek fault strand decreases as slip is transferred to the Banning fault strand in the central Indio Hills. However, our new results from uranium-series dating of pedogenic carbonate and 10Be cosmogenic exposure dating of surface clasts from four different deposits offset during three intervals since ~90 ka indicate that slip on the Mission Creek fault strand in the central Indio Hills has occurred at a relatively constant and unexpectedly fast rate of ~22-25 mm/yr and that slip on the Banning fault strand at this latitude has occurred a relatively slow rate of ~0.1-0.6 mm/yr since ~60 ka.
Intellectual Merit Our new results summarized above suggest an alternative kinematic model for the southern SAFZ: a fast slip rate on the Mission Creek fault strand and a slow slip rate on the Banning fault strand, as the two strands diverge from each other in the southern Indio Hills. In this alternative model, a SAFZ earthquake may rupture on the Mission Creek fault strand rather than the Banning fault strand. These new data underscore the seismic hazard posed by the Mission Creek fault strand in this region. For instance, combining these data with published paleoseismic studies for the Mission Creek fault strand at Thousand Palms, which show an average earthquake recurrence interval of 225 years for the past 5 events since 900 AD (Fumal et al., 2002) implies an average slip per event of ~4.5 m. As the last earthquake to rupture this section of the Mission Creek fault occurred over 300 years ago (ca. 1690), the results of our work indicate that ca. 6.0 to 7.5 m of strain has accumulated since that event. Therefore, additional work is needed to better understand how slip along the SAFZ is partitioned within the northwestern Indio Hills and as the fault enters the San Gorgonio Pass
Broader Impacts The project promoted collaborations between three different institutions including the USGS, Berkeley Geochronology Center and the University of California Berkeley. The lead scientist, Kimberly Blisniuk is an early career female scientist.
Exemplary Figure Figure 2Left panel, present-day image of beheaded channels (C1, C2, C3) with their corresponding terrace (T1, T2, and T3) offset along the Mission Creek fault strand (red line) in the central Indio Hills, see Figure 1 for location. Black numbers are ages determined for terraces and channel deposits. Red arrows show the offsets measured. Right panel, field photo of terraces inset into older terraces preserved in Pushawalla Canyon. Ages summarized are the oldest ages determined from 10Be exposure dating or U-series dating of pedogenic carbonate.