A fault and seismicity based composite simulation in northern California

Abstract

Abstract. We generate synthetic catalogs of seismicity in northern California using a composite simulation. The basis of the simulation is the fault based "Virtual California" (VC) earthquake simulator. Back-slip velocities and mean recurrence intervals are specified on model strike-slip faults. A catalog of characteristic earthquakes is generated for a period of 100 000 yr. These earthquakes are predominantly in the range M = 6 to M = 8, but do not follow Gutenberg-Richter (GR) scaling at lower magnitudes. In order to model seismicity on unmapped faults we introduce background seismicity which occurs randomly in time with GR scaling and is spatially associated with the VC model faults. These earthquakes fill in the GR scaling down to M = 4 (the smallest earthquakes modeled). The rate of background seismicity is constrained by the observed rate of occurrence of M > 4 earthquakes in northern California. These earthquakes are then used to drive the BASS (branching aftershock sequence) model of aftershock occurrence. The BASS model is the self-similar limit of the ETAS (epidemic type aftershock sequence) model. Families of aftershocks are generated following each Virtual California and background main shock. In the simulations the rate of occurrence of aftershocks is essentially equal to the rate of occurrence of main shocks in the magnitude range 4 < M < 7. We generate frequencymagnitude and recurrence interval statistics both regionally and fault specific. We compare our modeled rates of seismicity and spatial variability with observations.

Multi-scale rupture growth with alternating directions in a complex fault network during the 2023 south-eastern Türkiye and Syria earthquake doublet

“…The geometric complexity of the EAF and the adjacent fault networks, apparent offset of the initial M 7.7 epicenter from the main EAF strand, high non-double couple components of the GCMT solutions, and the aftershock distribution with diverse orientations collectively suggest the earthquake sequence may have involved complexity of both the rupture evolution and fault geometry (Abercrombie et al, 2003;Okuwaki et al, 2021;. In general, geometric complexities of a fault system are known to control rupture speed and direction, and triggering of separated fault segments (Das & Aki, 1977;Kase & Day, 2006;Yıkılmaz et al, 2015;. There is also growing observational evidence of rupture irregularity in the complex fault damage zones in different tectonic regimes, such as transient supershear ruptures across fault bends (Bao et al, 2019;Socquet et al, 2019), triggering of ruptures with different faulting styles and on different segments (Nissen et al, 2016;, and apparent rupture back-propagation or re-rupture (Hicks et al, 2020;Vallée et al, 2023;Yagi et al, 2023).…”

Complexity and Earthquakes

“…A California fault model includes about 180 faults and fault segments. Yikilmaz et al (2011) generated synthetic catalogs of seismicity in northern California using a composite simulation of earthquakes. In order to constrain the behavior of the faults, a mean slip velocity and a mean recurrence interval between earthquakes are prescribed for all faults and fault segments.…”

Record-Breaking Intervals: Detecting Trends in the Incidence of Self-Similar Earthquake Sequences

“…It may be possible to estimate earthquake incidence by convolving RBTS with epidemic type aftershock sequence (ETAS)-based models (OGATA, 1988;YODER et al, 2012bYODER et al, , 2014a. More sophisticated physics-based earthquake simulators, for example Virtual California (VC) (YIKILMAZ et al, 2010(YIKILMAZ et al, , 2011RUNDLE et al, 2006) seem to be an increasingly attractive option. Rather than directly estimating failure from time-series data, these simulators can be parameterized from RBTS (and other) data and run forward to produce synthetic catalogs which can be aggregated and assessed by use of different established back-testing methods USGS-CSEP, 2013;JOLLIFFE and STEPHENSON, 2003).…”