A 15 year catalog of more than 1 million low‐frequency earthquakes: Tracking tremor and slip along the deep San Andreas Fault

Shelly, D. R.

doi:10.1002/2017jb014047

Cited by 71 publications

(165 citation statements)

References 67 publications

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“…The catalog includes over one million earthquakes recorded since 2001; however, we limit our analysis to between 2006 and May of 2016 to minimize the effect of afterslip from the 2004 M6 Parkfield earthquake. Additionally, estimated LFE source dimensions of hundreds of meters (e.g., Bostock et al, 2015;Thomas et al, 2016) are typically less than LFE location uncertainties of 1-2 km (Shelly, 2017). The time series of cross correlations for each template are then summed over each station and channel to create a network cross-correlation time series.…”

Section: Methodsmentioning

confidence: 99%

“…The LFE catalog used in this study can be found in the supporting information of Shelly (2017). A. M. T. and Q.…”

Section: Acknowledgmentsmentioning

confidence: 99%

“…For example, long-duration, small-amplitude seismic signals, dubbed nonvolcanic tremor (NVT) or tectonic tremor, usually lack the obvious impulsive phase arrivals associated with regular earthquakes and are depleted in high-frequency content relative to conventional earthquakes of the same moment Obara, 2002). Similar analysis was later applied to tremor on the Parkfield section of the San Andreas Fault (SAF), which has produced a catalog of over one million LFEs detected between 2001 and 2016 grouped into 88 different families based on waveform similarity between events (Shelly, 2017). Shelly et al (2007) demonstrated that the NVT signal in Japan can be explained as a superposition of many LFEs.…”

Section: Introductionmentioning

confidence: 99%

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Using Low‐Frequency Earthquake Families on the San Andreas Fault as Deep Creepmeters

et al. 2018

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The central section of the San Andreas Fault hosts tectonic tremor and low‐frequency earthquakes (LFEs) similar to subduction zone environments. LFEs are often interpreted as persistent regions that repeatedly fail during the aseismic shear of the surrounding fault allowing them to be used as creepmeters. We test this idea by using the recurrence intervals of individual LFEs within LFE families to estimate the timing, duration, recurrence interval, slip, and slip rate associated with inferred slow slip events. We formalize the definition of a creepmeter and determine whether this definition is consistent with our observations. We find that episodic families reflect surrounding creep over the interevent time, while the continuous families and the short time scale bursts that occur as part of the episodic families do not. However, when these families are evaluated on time scales longer than the interevent time these events can also be used to meter slip. A straightforward interpretation of episodic families is that they define sections of the fault where slip is distinctly episodic in well‐defined slow slip events that slip 16 times the long‐term rate. In contrast, the frequent short‐term bursts of the continuous and short time scale episodic families likely do not represent individual creep events but rather are persistent asperities that are driven to failure by quasi‐continuous creep on the surrounding fault. Finally, we find that the moment‐duration scaling of our inferred creep events are inconsistent with the proposed linear moment‐duration scaling. However, caution must be exercised when attempting to determine scaling with incomplete knowledge of scale.

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Section: Methodsmentioning

confidence: 99%

“…The LFE catalog used in this study can be found in the supporting information of Shelly (2017). A. M. T. and Q.…”

Section: Acknowledgmentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Using Low‐Frequency Earthquake Families on the San Andreas Fault as Deep Creepmeters

et al. 2018

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“…The semidiurnal period is more than 2 orders of magnitude longer than the average episode duration of 302 s, meaning that to first order, all of the LFEs in each episode occur at the same time relative to the tidal period. To avoid possible influences of the 2004 Parkfield earthquake (e.g., Shelly, 2017) we undertake the analysis from 2005.5 (07/02/05) to the end of the catalog (1/4/2012). The average recurrence interval in this family is 3.4 days, intermediate between the semidiurnal and fortnightly tides.…”

Section: Catalog Processingmentioning

confidence: 99%

“…The central San Andreas LFE catalog (Shelly & Hardebeck, 2010;Shelly, 2017) was used in this paper. That data and the technical aspects of catalog generation are available in those publications and their supplements.…”

Section: Acknowledgmentsmentioning

confidence: 99%

Constraints on Friction, Dilatancy, Diffusivity, and Effective Stress From Low‐Frequency Earthquake Rates on the Deep San Andreas Fault

et al. 2018

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Families of recurring low‐frequency earthquakes (LFEs) within nonvolcanic tremor on the San Andreas Fault in central California are sensitive to tidal stresses. LFEs occur at all levels of the tides, are strongly correlated and in phase with the ~200 Pa shear stresses, and weakly and not systematically correlated with the ~2 kPa tidal normal stresses. We assume that LFEs are small sources that repeatedly fail during shear within a much larger scale, aseismically slipping fault zone and consider two different models of the fault slip: (1) modulation of the fault slip rate by the tidal stresses or (2) episodic slip, triggered by the tides. LFEs are strongly clustered with duration much shorter than the semidiurnal tide; they cannot be significantly modulated on that time scale. The recurrence times of clusters, however, are many times longer than the semidiurnal, leading to an appearance of tidal triggering. In this context we examine the predictions of laboratory‐observed triggered frictional (dilatant) fault slip. The undrained end‐member model produces no sensitivity to the tidal normal stress, and slip onsets are in phase with the tidal shear stress. The tidal correlation constrains the diffusivity to be less than ~1 × 10−6/s and the product of the friction and dilatancy coefficients to be at most 5 × 10−7, orders of magnitude smaller than observed at room temperature. In the absence of dilatancy the effective normal stress at failure would be about ~55 kPa. For this model the observations require intrinsic weakness, low dilatancy, and lithostatic pore fluid.

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Modeling Low‐Frequency Earthquake Recurrence Patterns

Daub

2017

Geophysical Research Letters

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Tectonic tremor and low-frequency earthquakes (LFE) have been identified globally, but the physical mechanisms responsible for different types of LFE recurrence patterns are still elusive. Here we use a brittle ductile friction model to study the frictional conditions leading to different LFE recurrence patterns observed in central California. We do a comprehensive search of the friction parameters, including the brittle contact failure length and ductile damping strength to generate synthetic LFE bursts that match three different occurrence patterns of LFE bursts. We find that the output synthetic LFE burst recurrence type varies under different frictional conditions. The chaotic recurrence LFE sources require a higher brittle-to-ductile friction ratio, consistent with the observation that they are mainly at shallower part of the brittle-ductile transition zone. The trimodal recurrence LFE sources require a wide distribution of asperity sizes, indicating that the segment of deep San Andreas Fault between Monarch Peak and Parkfield is likely to be more fragmented and weaker than the surrounding segments. 2. Brittle-Ductile Friction Model We employ a brittle-ductile friction model developed by Daub et al. (2011) to investigate the LFE recurrence patterns. In the model, a block on a surface is driven by a spring that represents the tectonic loading of the WU AND DAUB MODELING LFE RECURRENCE PATTERNS 10,970

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A 15 year catalog of more than 1 million low‐frequency earthquakes: Tracking tremor and slip along the deep San Andreas Fault

Cited by 71 publications

References 67 publications

Using Low‐Frequency Earthquake Families on the San Andreas Fault as Deep Creepmeters

Using Low‐Frequency Earthquake Families on the San Andreas Fault as Deep Creepmeters

Constraints on Friction, Dilatancy, Diffusivity, and Effective Stress From Low‐Frequency Earthquake Rates on the Deep San Andreas Fault

Modeling Low‐Frequency Earthquake Recurrence Patterns

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