A unified perspective of seismicity and fault coupling along the San Andreas Fault

Abstract

The San Andreas Fault (SAF) showcases the breadth of possible earthquake sizes and occurrence behavior; in particular, the central SAF is a microcosm of such diversity. This section also exhibits the spectrum of fault coupling from locked to creeping. Here, we show that the observations of aseismic slip, temporal clustering of seismicity, and spatial variations in earthquake size distributions are tightly connected. Specifically, the creep rate along the central SAF is shown to be directly proportional to the fraction of nonclustered earthquakes for the period 1984–2020. This relationship provides a unified perspective of earthquake phenomenology along the SAF, where lower coupling manifests in weaker temporal clustering, with repeating earthquakes as an end-member. This new paradigm provides additional justification for characterizing the northwest ∼75 kilometers of the creeping segment as a transition zone, with potential implications for seismic hazard.

Spatiotemporal Evolution of the Seismicity in the Alto Tiberina Fault System Revealed by a High‐Resolution Template Matching Catalog

“…Together with the short bursts of events along the LANF (Figure 6c), we observe the occurrence of long‐term and nearly continuous seismicity. This seismicity seems to agree with creep (Liu et al., 2022), as proposed by Anderlini et al. (2016).…”

“…Together with the short bursts of events along the LANF (Figure 6c), we observe the occurrence of long-term and nearly continuous seismicity. This seismicity seems to agree with creep (Liu et al, 2022), as proposed by Anderlini et al (2016). However, unlike many other well-instrumented creeping faults (e.g., Nadeau & McEvilly, 1999;Uchida, 2019;Uchida & Bürgmann, 2019), we found no evidence of RE sequences (Figure 7).…”

“…We begin the analysis by assessing the interaction in time and space between seismic events. The presence (absence) of earthquakes clustering provides fundamental insights into the dynamics of seismicity and rheological properties of fault systems, as revealed from seismological studies (Liu et al., 2022) and numerical modeling (Dublanchet et al., 2013). The simplest mechanism of time and space clustering of earthquakes is through interactions between events during co‐ and post‐seismic processes, like static or dynamic stress transfer triggering (Freed, 2005) or afterslip (Perfettini & Avouac, 2004), with additional modulation related to the asperity density (Dublanchet et al., 2013).…”

Seismicity, Fault Architecture, and Slip Mode of the Westernmost Gofar Transform Fault

“…Fault architecture and slip mode partition are imprinted in microearthquakes (Y. K. Liu et al., 2022; Vidale et al., 1994). Particularly, interaction and triggering among different fault segments are often manifested as transient earthquake sequences lasting from seconds to years (Freed, 2005).…”

“…Both seismic and aseismic slip can consume the total slip budget to accommodate plate motions (Avouac, 2015; Harris, 2017; Wolfson‐Schwehr & Boettcher, 2019). The two slip modes dominate different fault patches and show variations along both the strike and dip directions (e.g., Han et al., 2017; Y. Liu & Rice, 2005; Y. K. Liu et al., 2022; Scholz, 1998). For example, earthquakes and slow earthquakes occur at subduction zone with different types of events dominating megathrust segments at varying depths (Lay et al., 2012; Obara & Kato, 2016; Wirth et al., 2022).…”