A Geodesy‐ and Seismicity‐Based Local Earthquake Likelihood Model for Central Los Angeles

Abstract

We estimate time‐independent earthquake likelihoods in central Los Angeles using a model of interseismic strain accumulation and the 1932–2017 seismic catalog. We assume that on the long‐term average, earthquakes and aseismic deformation collectively release seismic moment at a rate balancing interseismic loading, mainshocks obey the Gutenberg‐Richter law (a log linear magnitude‐frequency distribution [MFD]) up to a maximum magnitude and a Poisson process, and aftershock sequences obey the Gutenberg‐Richter and “Båth” laws. We model a comprehensive suite of these long‐term systems, assess how likely each system would be to have produced the MFD of the instrumental catalog, and use these likelihoods to probabilistically estimate the long‐term MFD. We estimate Mmax = 6.8 + 1.05/−0.4 (every ~300 years) or Mmax = 7.05 + 0.95/−0.4 assuming a truncated or tapered Gutenberg‐Richter MFD, respectively. Our results imply that, for example, the (median) likelihood of one or more Mw ≥ 6.5 mainshocks is 0.2% in 1 year, 2% in 10 years, and 18–21% in 100 years.

Accommodation of Plate Motion in an Incipient Strike‐Slip System: The Central Walker Lane

“…As geodesy is increasingly used to inform seismic hazards (e.g., Field et al., 1999; Petersen et al., 2014; Riguzzi et al., 2012; Rollins & Avouac, 2019; Wesnousky et al., 2012), it is important to understand how geodetic observations relate to paleoseismic evidence preserved in the geologic record. In the Central Walker Lane, between the latitudes of Lake Tahoe and Walker Lake (Figure 1), GPS measurements indicate that the Walker Lane accommodates ∼7 mm/yr of northwest directed dextral shear (Bormann et al., 2016; Hammond & Thatcher, 2005, 2007; Hammond et al., 2011; Thatcher et al., 1999).…”

Seismogenic Potential of the Main Himalayan Thrust Constrained by Coupling Segmentation and Earthquake Scaling

“…We combine the PDF of seismic models that satisfy the moment budget and the MFD of the current and historical catalogs with that of the physical consistency of earthquakes, and evaluate the marginal PDF of the maximum magnitude earthquake and of its recurrence time. Finally, from , thus knowing the earthquake rate of each magnitude for each seismicity model and their related probability to be plausible, we calculate the probability to have an earthquake over a certain magnitude for a given period of time, (Michel et al., 2018; Rollins & Avouac, 2019). Such estimates are important inputs for seismic hazard mapping.…”

Seismogenic potential of the Main Himalayan Thrust constrained by coupling segmentation and earthquake scaling

“…The first, which we call a truncated model, is a cumulative power-law MFD (the Gutenberg-Richter law) truncated at max M (e.g., Avouac, 2015;Michel et al, 2018;. The second, which we call a tapered model, is formed from truncating an incremental power-law MFD at max M , and has a tapered form in cumulative magnitude-log-frequency space (Rollins and Avouac, 2019, Supporting Information Text S2, Figure S2). Note that it is not the same as the tapered model used by (Kagan & Jackson, 2000) and subsequent studies.…”

“…The catalog-based probability Cat P for each model is then the product of these probabilities over the magnitude bins. In this way, we probabilistically estimate the long-term earthquake rates at each magnitude based on the moment budget and seismic catalog (Michel et al, 2018;Rollins & Avouac, 2019).…”

“…Following the elastic rebound hypothesis (Reid, 1910), the moment deficit accumulated during the interseismic period should be balanced on the long-term average by the moment released by earthquakes and aseismic slip (Avouac, 2015;Molnar, 1979). Evaluating this "moment budget" can provide first-order estimates of a regions seismic potential (e.g., Michel et al, 2018;Rollins & Avouac, 2019;Rong et al, 2014;Shen et al, 2007;.…”