Northern California Earthquake Geology Active
The principal faults of the San Andreas Fault (SAF) system and Pacific-North American plate boundary in northern California pose significant hazard to people, infrastructure, and the economy. Interestingly, in the later twentieth and early twenty-first centuries, the earthquakes that have affected the United States most significantly have not ruptured the primary faults of the greater SAF system known to accommodate most plate motions, but rather have occurred on a wide variety of smaller faults.
Geological research allows us to characterize the faults of northern California, including the identification of secondary seismogenic structures, to study how fault zones evolve, and to characterize how tectonics are recorded in the geologic record and on the landscape. Overall plate boundary deformation in California is well-constrained but understanding how these deformation rates are distributed across the complex fault network in time and space requires significant additional work.
The project is a multidisciplinary effort to improve the understanding of the active faults in northern California, refine our characterization of the geological manifestations of earthquake behavior, and to advance the science of earthquake geology and tectonic geomorphology. This is being accomplished through a focused integration of paleoseismic and other geologic studies, as well as with studies of ongoing crustal deformation as expressed at the Earth's surface. Project activities include: 1) determining the timing and size of large prehistoric earthquakes and fault slip rates for faults in northern California; 2) reducing uncertainties in recurrence, slip rate, and segmentation parameters used in models of seismic hazard; 3) developing slip rates and hazard estimates for poorly understood reverse, normal, and blind faults; 4) producing new Quaternary fault maps utilizing airborne lidar, terrestrial lidar, and UAV photogrammetric data for the region; 5) developing new methods for quantification of surface deformation and landscape change using lidar and photogrammetry; 6) obtaining fundamental fault behavior information from study of major faults and historical surface ruptures outside of northern California; 7) preparing for and responding to the next surface rupturing earthquake in northern California and preparing to contribute to earthquake response elsewhere in the U.S. and potentially internationally.
Results from this project are incorporated into hazard models and USGS products that include scientific literature, fault maps, and other publications and presentations that report slip rates, earthquake chronologies, and the distribution of fault creep across northern California. These are used by regulators, utilities, educators, and citizens to support decision-making. This includes decisions that are made regarding how northern Californians live and build seismic resilience into infrastructure and other physical and social systems.
An estimated $80 billion has been invested in a wide range of seismic retrofitting and to improve resilience of key infrastructure and lifelines in northern California since the 1989 Loma Prieta earthquake. Decisions and planning continue to be made based on knowledge of fault locations and their associated seismic hazard, much of which comes from this project and its extensive network of collaborators.
- Overview
The principal faults of the San Andreas Fault (SAF) system and Pacific-North American plate boundary in northern California pose significant hazard to people, infrastructure, and the economy. Interestingly, in the later twentieth and early twenty-first centuries, the earthquakes that have affected the United States most significantly have not ruptured the primary faults of the greater SAF system known to accommodate most plate motions, but rather have occurred on a wide variety of smaller faults.
Sources/Usage: Public Domain. View Media DetailsBelle Philibosian in a trench investigating the West Napa Fault near St. Helena, California, August 2017. Geological research allows us to characterize the faults of northern California, including the identification of secondary seismogenic structures, to study how fault zones evolve, and to characterize how tectonics are recorded in the geologic record and on the landscape. Overall plate boundary deformation in California is well-constrained but understanding how these deformation rates are distributed across the complex fault network in time and space requires significant additional work.
The project is a multidisciplinary effort to improve the understanding of the active faults in northern California, refine our characterization of the geological manifestations of earthquake behavior, and to advance the science of earthquake geology and tectonic geomorphology. This is being accomplished through a focused integration of paleoseismic and other geologic studies, as well as with studies of ongoing crustal deformation as expressed at the Earth's surface. Project activities include: 1) determining the timing and size of large prehistoric earthquakes and fault slip rates for faults in northern California; 2) reducing uncertainties in recurrence, slip rate, and segmentation parameters used in models of seismic hazard; 3) developing slip rates and hazard estimates for poorly understood reverse, normal, and blind faults; 4) producing new Quaternary fault maps utilizing airborne lidar, terrestrial lidar, and UAV photogrammetric data for the region; 5) developing new methods for quantification of surface deformation and landscape change using lidar and photogrammetry; 6) obtaining fundamental fault behavior information from study of major faults and historical surface ruptures outside of northern California; 7) preparing for and responding to the next surface rupturing earthquake in northern California and preparing to contribute to earthquake response elsewhere in the U.S. and potentially internationally.
Results from this project are incorporated into hazard models and USGS products that include scientific literature, fault maps, and other publications and presentations that report slip rates, earthquake chronologies, and the distribution of fault creep across northern California. These are used by regulators, utilities, educators, and citizens to support decision-making. This includes decisions that are made regarding how northern Californians live and build seismic resilience into infrastructure and other physical and social systems.
An estimated $80 billion has been invested in a wide range of seismic retrofitting and to improve resilience of key infrastructure and lifelines in northern California since the 1989 Loma Prieta earthquake. Decisions and planning continue to be made based on knowledge of fault locations and their associated seismic hazard, much of which comes from this project and its extensive network of collaborators.
Sources/Usage: Public Domain. View Media DetailsLooking south along the creeping section of the San Andreas Fault near Bitterwater, California, September 23, 2019.
Sources/Usage: Public Domain. View Media DetailsUSGS Geologists R. Sickler, J. Willard, and B. Philibosian observe as an excavator digs a pit used to investigate sediments uplifted by active tectonic activity in the San Joaquin – Sacramento Delta, California, November 29, 2021.
Sources/Usage: Public Domain. View Media DetailsUSGS Geologist S. Hecker examines sediments exposed in excavation along the Rodgers Creek fault near Windsor, California.