Research ArticleGEOPHYSICS

Connecting a broad spectrum of transient slip on the San Andreas fault

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Science Advances  14 Aug 2020:
Vol. 6, no. 33, eabb2489
DOI: 10.1126/sciadv.abb2489
  • Fig. 1 Tectonic context and LFEs’ spatiotemporal behavior.

    (A) Map view. Black dots show LFE locations. Magenta dots show 10 LFE families that Rousset et al. (7) used as guide to stack GPS time series and extract slow-slip deformation signal. Red dot shows LFE family previously suggested to be isolated (26). Gray dots show regular earthquakes in the region from 1984 to 2011 (44). Inset shows geographical location of Parkfield. (B) Along-fault cross section. Yellow star shows hypocenter of the 2004 Mw 6.0 Parkfield earthquake. (C) Space-time plot of the LFEs. Black dots show all events over an 8-day period. Colored dots show a few example clusters during this time period; events of the same color belong to the same cluster.

  • Fig. 2 LFE clustering properties.

    (A) g as a function of time. Red dashed line shows least-squares fit giving gt−1.8. (B) K as a function of distance. Since the absolute K value is affected by the LFE family size, we account for this effect by multiplying Kxy by nynx, where nx is the number of events from the excited family x and ny is the number of events from the exciting family y, before calculating the mean K value for different interfamily distance bins. Red dashed lines show least-squares fits giving Kd−2.8 and Kd−2.5 for along-strike and along-dip distances, respectively.

  • Fig. 3 SSE scaling properties.

    (A) Noncumulative magnitude-frequency distribution of the SSEs. Black circles show the number of SSEs in different Mw bins. Red dashed line shows maximum-likelihood fit giving a b value of 1.61. (B) Relationship between seismic moment (Mo) and rupture area (A) of SSEs. Black circles show the median A for different Mo bins. Red dashed line shows least-squares fit giving MoA1.5. Blue dashed lines show the MoA1.5 theoretical scaling relationships for circular cracks with different constant stress drops (38). (C) Histogram of SSE duration. Blue vertical line marks the local minimum used to separate the two populations of SSEs. (D) Relationship between Mo and duration (T) of SSEs. Blue horizontal line is the same duration boundary as in (C) that is used to separate the SSEs into two populations. For each SSE population, black circles show the median T for different Mo bins. Red dashed lines show least-squares fits giving MoT3.1 and MoT2.8 for the shorter- and longer-duration SSE populations, respectively.

  • Fig. 4 Comparison between slow events on the San Andreas fault and proposed moment-duration scaling for regular (green bar) and slow (blue bar) earthquakes (12).

    Green circles, two LFE families (41); magenta circle, episodic creep events (45); blue circle, slow earthquake (46); red circle, average of 20 SSEs (7); black circles, SSEs in this study (same as in Fig. 3D).

Supplementary Materials

  • Supplementary Materials

    Connecting a broad spectrum of transient slip on the San Andreas fault

    Yen Joe Tan and David Marsan

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