Millennial to million year slip-rate variations on active faults

Vasiliki Mouslopoulou, Andy Nicol, & John Walsh

Published July 27, 2020, SCEC Contribution #10211, 2020 SCEC Annual Meeting Talk on TBD

Fault growth is typically achieved by discrete increments of slip which accrue during earthquakes. Comparison of geologically short-term (200 yrs to 20 kyr) displacements from individual earthquakes or active scarps with geologically long-term (>20 kyr) fault displacement patterns permits characterization of fault growth from millennial to million-year timescales. Fault slip distribution during individual earthquakes is generally more variable than would be predicted from fault growth studies on geological timescales, which indicates near-constant growth rates. Displacement rates on individual faults are found to depart from their million-year average rates by up to three orders of magnitude with the size of these departures inversely related to sampling length scales (temporal and/or spatial) and to fault length. Time-variable displacement rates are primarily ascribed to temporal clustering of large-magnitude (M>6) earthquakes on individual faults coupled with biases associated with sampling of faults that have moved faster recently (i.e. the last 10 ka). The increased stability of fault displacement rates at greater temporal and spatial scales suggests that each fault is a component of a kinematically coherent system in which all faults interact and their earthquake histories are interdependent. Where the boundary conditions of fault systems are stable, displacement rates generally become constant over time periods between 20 and 300 ka, with the length of time required to reach stability being inversely related to the magnitude of regional strain rates. The long-term stability and short-term variability of displacement rates are both partly due to fault interactions, which may produce non-characteristic seismic slip, variable rupture lengths and aperiodic earthquake recurrence.

Key Words
Active faults, Paleoearthquakes, Slip-rates, Holocene, Earthquake Recurrence, Timescale

Mouslopoulou, V., Nicol, A., & Walsh, J. (2020, 07). Millennial to million year slip-rate variations on active faults. Oral Presentation at 2020 SCEC Annual Meeting.

Related Projects & Working Groups
Stress and Deformation Over Time (SDOT)