Testing the repetitiveness of repeating earthquakes: Analyzing spatiotemporal changes of repeating earthquake characteristics in response to seismicity

Norma A. Contreras, Gareth J. Funning, & Rachel E. Abercrombie

Published September 8, 2024, SCEC Contribution #14000, 2024 SCEC Annual Meeting Poster #055

Understanding the factors that influence earthquake recurrence is important for hazard and risk assessment, but the long recurrence times for larger events make it difficult to analyze the factors affecting their recurrence. We use repeating earthquake sequences (RES) of smaller earthquakes to analyze the factors affecting their periodicity. Repeating earthquakes are collocated events with nearly identical waveforms that exhibit quasi-periodic behavior. Previous studies have found that large magnitude events can alter the behavior and source characteristics of events in a RES, such as increasing magnitude with a decreasing recurrence interval, a change that has been attributed to the increase, and then decay of loading rate following a large-magnitude event. These changes, however, have been found to vary across RES, with some disappearing or decreasing in magnitude. We explore this further by studying whether RES (M≤3.4) on the Calaveras and San Andreas faults react to moderate magnitude earthquakes (M3.5-5.0) in their vicinity, examining spatiotemporal changes in RES at both the fault and individual sequence scales. We used the FARESearch (Funning and Shakibay Senobari 2021) method to create repeating earthquake catalogs for the Calaveras fault and San Juan Bautista and Parkfield segments of the central San Andreas fault. We limit our study to ~2,000 RES with at least five events and a minimum duration of five years. We investigate their response to local earthquakes, of different magnitude and distance, analyzing trends in recurrence intervals, periodicity, magnitude, depth, and number of events in a RES. The distribution and broad characteristics of the RES show no clear dependence on depth or location between the three segments. At a smaller scale, we find evidence of various behaviors. For example, two RES on the San Juan Bautista segment appear to experience a shortened recurrence interval following a series of M3.5-5 events within 4 and 8 km. We also find sequences that do not appear to respond to nearby events of similar magnitudes. Our next step is to combine our catalogs with published RES catalogs to ensure a robust repeating earthquake catalog for our study regions. We will conduct a systematic analysis of RES responses to nearby, moderate earthquakes as a function of the latter’s magnitude and distance, helping us constrain a model that can explain the range and pattern of observed behaviors.

Key Words
repeating earthquakes, earthquake periodicity

Citation
Contreras, N. A., Funning, G. J., & Abercrombie, R. E. (2024, 09). Testing the repetitiveness of repeating earthquakes: Analyzing spatiotemporal changes of repeating earthquake characteristics in response to seismicity. Poster Presentation at 2024 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology