Project Grant G25AP00382

PROJECT TITLE: A PALEOSEISMIC INVESTIGATION OF THE SHIVELY FAULT ZONE, COLLABORATIVE RESEARCH WITH THE CALIFORNIA GEOLOGICAL SURVEY, CAL POLY HUMBOLDT, AND THE U.S. GEOLOGICAL SURVEYPROJECT PERIOD: 9 1 2025 THROUGH 8 31 2026AWARD PURPOSE: SEISMIC HAZARDS IN COASTAL NORTHERN CALIFORNIA ARE CONTROLLED BY TWO OVERLAPPING PLATE BOUNDARY SYSTEMS, THE CASCADIA SUBDUCTION ZONE AND THE SAN ANDREAS FAULT SYSTEM, WHICH MEET IN THE MENDOCINO TRIPLE JUNCTION REGION. THIS PROPOSED PROJECT LIES IN THIS REGION. CRUSTAL FAULTS IN THIS REGION POSE A RISK TO THE COMMUNITIES OF EUREKA, ARCATA, FORTUNA, AND DOZENS OF UNDERSERVED COMMUNITIES IN CENTRAL HUMBOLDT COUNTY. THERE IS EXISTING INFRASTRUCTURE (HIGHWAYS, UTILITIES, ETC.) AND POTENTIAL WIND-ENERGY 500 KV TRANSMISSION LINE INFRASTRUCTURE THAT WILL BE AT RISK. CURRENTLY, THESE FAULTS ARE POORLY UNDERSTOOD COMPARED TO THE CASCADIA SUBDUCTION ZONE AND SAN ANDREAS FAULT SYSTEMS. THE RECIPIENT WILL INVESTIGATE THE SHIVELY FAULT ONE OF THESE CRUSTAL FAULTS IN THE MENDOCINO TRIPLE JUNCTION REGION. THERE REMAINS CONSIDERABLE UNCERTAINTY ABOUT ITS SLIP RATE, SENSE OF MOTION, SLIP PER EVENT, AND EARTHQUAKE RECURRENCE INFORMATION. FOR THIS PILOT STUDY, WE PROPOSE TO COLLECT SEDIMENTARY STRATIGRAPHIC AND FAULT TRENCH EXCAVATION OBSERVATIONS TO ESTABLISH A BASIC FRAMEWORK FOR THESE TYPES OF DATA. THIS IS THE FIRST OF MANY FUTURE STUDIES THAT WILL BE REQUIRED BEFORE THE RECIPIENT HAS A COMPREHENSIVE UNDERSTANDING OF THE SEISMIC HAZARDS FOR THIS REGION. QUATERNARY FLUVIAL TERRACES ALONG THE EEL RIVER NEAR THE TOWN OF SHIVELY APPEAR OFFSET ALONG TOPOGRAPHIC SCARPS. THE SCARPS ARE SOUTH FACING AND HAVE INCREASING HEIGHTS ASSOCIATED WITH OLDER AND HIGHER TERRACE TREADS (SCARP SIZE SCALES WITH AGE AND IS EVIDENCE FOR GROWTH OVER TIME). THE RECIPIENT WILL HYPOTHESIZE THAT THESE SCARPS ARE FORMED BY EARTHQUAKE SLIP ALONG THE SHIVELY FAULT.IF THE RESULTS SUPPORT OUR HYPOTHESES, THE IMPLICATIONS ARE THAT WE WILL IMPROVE THE ESTIMATE OF THE SIZE, RECURRENCE INTERVAL, AND EFFECTS OF PAST, LATE QUATERNARY CRUSTAL EARTHQUAKES IN THE MENDOCINO TRIPLE JUNCTION REGION. THIS INFORMATION CAN BE USED TO TEST THE HYPOTHESIS THAT THE SHIVELY FAULT IS A SOURCE OF SEISMIC HAZARD.ACTIVITIES TO BE PERFORMED SEDIMENT CORING - AT LOCATIONS ON EITHER SIDE OF THE SCARPS IN TERRACE DEPOSITS. TRENCH EXCAVATION - AT TWO LOCATIONS TO EXPOSE FAULTED TERRACE DEPOSITS. GEOCHRONOLOGICAL ANALYSES - OF FAULTED AND UNFAULTED TERRACE DEPOSITS AND FAULT ASSOCIATED DEPOSITS IN ORDER TO DEVELOP A CHRONOLOGY OF FAULT ACTIVITY.DELIVERABLES AND EXPECTED OUTCOMES DETERMINE IF THE SHIVELY FAULT HAS A RECORD OF LATE-QUATERNARY EARTHQUAKES DETERMINE WHEN AND HOW FREQUENTLY THESE EARTHQUAKES OCCURRED DETERMINE THE LATE-PLEISTOCENE TO HOLOCENE SLIP RATE AND SLIP-PER EVENT DATA FOR THE SHIVELY FAULT. COMPARE THE EARTHQUAKE CHRONOLOGY OF THE SHIVELY FAULT TO ASSESS WHETHER IT IS AN INDEPENDENT SEISMIC SOURCE, OR IF IT RUPTURES IN COINCIDENCE WITH THE CSZ OR THE SAF. FINAL REPORT. PEER REVIEWED PAPER. PRESENTATIONS TO THE RESIDENTS OF SHIVELY, TO CAL POLY HUMBOLDT GEOLOGY STUDENTS. PRESENTATION AT FORMAL SCIENTIFIC MEETING(S) SUCH AS THE AMERICAN GEOPHYSICAL UNION OR THE GEOLOGICAL SOCIETY OF AMERICA.INTENDED BENEFICIARY(IES) RESIDENTS AND VISITORS TO CENTRAL HUMBOLDT COUNTY. REAL ESTATE DEVELOPERS AND BUILDING CODE OFFICIALS IN CENTRAL HUMBOLDT COUNTY. CALIFORNIA GEOLOGICAL SURVEY AND U.S. GEOLOGICAL SURVEY (INGESTION OF NEW FAULT DATA INTO EXISTING FAULT DATABASES INGESTION OF SEISMIC HAZARDS DATA INTO FUTURE SEISMIC HAZARDS ANALYSES). SEISMIC HAZARD SCIENTISTS.SUBRECIPIENT ACTIVITIES: N A UNKNOWN