Then the team combined two different dating techniques - uranium-thorium dating of soil and beryllium-10 dating of surface exposures - to provide a minimum age estimate and a maximum age estimate for the landforms.
They used lidar imaging and field mapping to determine the offset of ancient stream channels and other landforms. Kimberly Blisniuk, an earthquake geologist and geochronologist at San Jose State University, and her team started by reconstructing and dating landform offsets in the Indio Hills (Banning) and Pushawalla Canyon (Mission Creek). The new study investigates the slip rates from two new locations in the valley. The Banning and Mission Creek strands run roughly parallel to one another. Previous geologic and geodetic data suggested that one piece of the San Andreas in the Coachella Valley called the Banning strand was likely responsible for the bulk of the slipping northwest through the San Gorgonio Pass. Geodetic data obtained by ground motion observed in GPS or radar imaging can also be used to model slip rates. Slip rates are typically ascertained through geologic measurements of landforms offset by fault movement, such as jags in alluvial fans, beheaded stream channels (those cut off from their headwaters), and vegetation lineaments (where dense vegetation meets less-dense vegetation in an abrupt line, likely due to a fault cutting off groundwater where the line occurs). Slip rates describe the speed at which the two sides of a fault move relative to each other. The Mission Creek strand may be a bigger risk for Southern California than previously thought. The southern San Andreas Fault consists of multiple strands. That means the Mission Creek strand - not the strands previously identified as accumulating the most strain - could host the next major earthquake on the southern San Andreas. This is partly why people often say it’s “overdue” for a big quake (though faults can’t really be overdue).Ī recent study published in Science Advances suggests that the Mission Creek strand of the San Andreas, which runs along the northeastern side of the Coachella Valley, is the dominant fault at this latitude, accounting for about 90% of the overall slip rate of the southern San Andreas Fault system. The southernmost section, southeast of Los Angeles, however, last ruptured in 1726 and has accumulated significant strain since. The northern and central sections of the San Andreas have ruptured relatively recently, geologically speaking (in 19, respectively), producing magnitude-7+ earthquakes (Fialko, 2006). But its southernmost section, which is divided into strands like the frayed ends of a rope, still puzzles scientists. Since its formal identification in the late 19th century, the fault has been analyzed, dated, mapped and modeled by thousands of scientists.
#San andreas fault map movie#
The San Andreas Fault is as close to a celebrity as geological features can get - it even has a movie named in its honor. A recent study indicates increased slip rates along the Mission Creek strand of the San Andreas Fault, suggesting a novel configuration of earthquake risk at this latitude.īy Ben Wolman, science writer Wolman, B, 2021, Surprising recharacterization of earthquake risk along a strand of the San Andreas, Temblor,