Superficial simplicity of the 2010 El Mayor–Cucapah earthquake of Baja California in Mexico

Wei, Shengji; Fielding, E. J.; Leprince, S.; Sladen, Anthony; Avouac, Jean Philippe; Helmberger, Donald V.; Hauksson, Egill; Chu, Risheng; Simons, M.; Hudnut, K. W.; Herring, T. A.; Briggs, Richard W.

doi:10.1038/ngeo1213

Cited by 242 publications

(319 citation statements)

References 25 publications

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“…4), although the seismic radiators associated with the two rupture fronts appear intermittently. The length of the northern branch is 60 km, consistent with finite-fault models (e.g., Wei et al, 2011). However, the southern rupture appears as only 20 km long, significantly shorter than that of the finite-fault models.…”

Section: Methodssupporting

confidence: 56%

“…This example again demonstrates the value of a network of multiple arrays along the length of active faults for real-time application of this method. Overall, the 80 km rupture length is shorter than the 120 km rupture length estimated by Wei et al (2011) but is still a reasonable estimate for EEW purpose and better than treating the event as a point source.…”

Section: Methodsmentioning

confidence: 94%

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Application of Seismic Array Processing to Earthquake Early Warning

Meng¹,

Allen²,

Ampuero³

2014

Bulletin of the Seismological Society of America

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Earthquake early warning (EEW) systems that issue warnings prior to the arrival of strong shaking are essential in mitigating earthquake hazard. Currently operating EEW systems work on point-source assumptions and are of limited effectiveness for large events, for which ignoring finite-source effects result in magnitude underestimation. Here, we explore the concept of characterizing rupture dimensions in real time for EEW using small-aperture seismic arrays located near active faults. Back tracing array waveforms allow estimation of the extent of the rupture front (as a proxy of the rupture size) and directivity in real time, providing complementary EEW capabilities for M > 7 earthquakes to existing EEW systems. We implement it in a simulated realtime environment and analyze the 2004 M 6 Parkfield, California, earthquake recordings by the U.S. Geological Survey Parkfield dense Seismograph ARray (UPSAR) array and the 2010 M 7.2 El Mayor-Cucapah earthquake recordings by strong-motion sensors in San Diego, California. We find it important to correct for the bias in back azimuth induced by dipping structures beneath the UPSAR array, based on data from smaller events. Our estimated rupture length is 30% shorter than those inferred from other studies but still reasonable for EEW purposes. We attribute this difference to rupture directivity effects and the limited field of view of a single array. The accuracy of the approach may be improved with a network of arrays with overlapping fields of view. We demonstrate this by tracking the 2011 Tohoku earthquake rupture with two clusters of Hi-net stations in Kyushu and northern Hokkaido. The obtained results are consistent with teleseismic back-projection results and yield reasonable estimates of rupture length and directivity. Compared with other proposed finite-fault EEW approaches, the array method is less affected by the coarseness of a Global Positioning System or seismic network and provides a high-frequency characterization of the rupture that yields more suitable predictors of ground shaking for certain structures.

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Section: Methodssupporting

confidence: 56%

Section: Methodsmentioning

confidence: 94%

Application of Seismic Array Processing to Earthquake Early Warning

Meng¹,

Allen²,

Ampuero³

2014

Bulletin of the Seismological Society of America

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“…Figure 2 shows pressure and strain time series at station B084 in Anza before, during, and after the 2010:094 M W 7.2 El Mayor Cucapah earthquake [Wei et al, 2011], which occurred ∼200 km from the Anza network (Table 1); these records demonstrate how an undrained pore pressure response is linearly proportional to areal strain from frequencies at least as low as atmospheric pressure changes to at least as high as strong regional body waves, as we should expect. But, as I shall show, the linear proportionality of excess pressure to areal strain (e.g., equation (6)) does not accurately describe all of the observations reported here.…”

Section: Relating Dynamic Pressures To Dynamic Strainsmentioning

confidence: 88%

Pore pressure sensitivities to dynamic strains: Observations in active tectonic regions

Barbour

2015

JGR Solid Earth

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Triggered seismicity arising from dynamic stresses is often explained by the Mohr‐Coulomb failure criterion, where elevated pore pressures reduce the effective strength of faults in fluid‐saturated rock. The seismic response of a fluid‐rock system naturally depends on its hydromechanical properties, but accurately assessing how pore fluid pressure responds to applied stress over large scales in situ remains a challenging task; hence, spatial variations in response are not well understood, especially around active faults. Here I analyze previously unutilized records of dynamic strain and pore pressure from regional and teleseismic earthquakes at Plate Boundary Observatory (PBO) stations from 2006 to 2012 to investigate variations in response along the Pacific/North American tectonic plate boundary. I find robust scaling response coefficients between excess pore pressure and dynamic strain at each station that are spatially correlated: around the San Andreas and San Jacinto fault systems, the response is lowest in regions of the crust undergoing the highest rates of secular shear strain. PBO stations in the Parkfield instrument cluster are at comparable distances to the San Andreas Fault (SAF), and spatial variations there follow patterns in dextral creep rates along the fault, with the highest response in the actively creeping section, which is consistent with a narrowing zone of strain accumulation seen in geodetic velocity profiles. At stations in the San Juan Bautista (SJB) and Anza instrument clusters, the response depends nonlinearly on the inverse fault‐perpendicular distance, with the response decreasing toward the fault; the SJB cluster is at the northern transition from creeping‐to‐locked behavior along the SAF, where creep rates are at moderate to low levels, and the Anza cluster is around the San Jacinto Fault, where to date there have been no statistically significant creep rates observed at the surface. These results suggest that the strength of the pore pressure response in fluid‐saturated rock near active faults is controlled by shear strain accumulation associated with tectonic loading, which implies a strong feedback between fault strength and permeability: dynamic triggering susceptibilities may vary in space and also in time.

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“…An extreme example is the 2010 M7.2 El-Mayor Cucapah earthquake in Northern Mexico which began as a smaller ∼M6 normal faulting quake and was followed ∼15 s later by the normal/strike-slip faulting main shock (Wei et al 2011;Böse et al 2015). EEW algorithms that are based only on the first few seconds of waveforms will likely fail to characterize events like El-Mayor.…”

Section: Discussionmentioning

confidence: 99%

FinDer v.2: Improved real-time ground-motion predictions for M2–M9 with seismic finite-source characterization

Böse¹,

Smith

Felizardo

et al. 2017

Geophysical Journal International

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S U M M A R YRecent studies suggest that small and large earthquakes nucleate similarly, and that they often have indistinguishable seismic waveform onsets. The characterization of earthquakes in real time, such as for earthquake early warning, therefore requires a flexible modeling approach that allows a small earthquake to become large as fault rupture evolves over time. Here, we present a modeling approach that generates a set of output parameters and uncertainty estimates that are consistent with both small/moderate (≤M6.5) and large earthquakes (>M6.5) as is required for a robust parameter interpretation and shaking forecast. Our approach treats earthquakes over the entire range of magnitudes (>M2) as finite line-source ruptures, with the dimensions of small earthquakes being very small (<100 m) and those of large earthquakes exceeding several tens to hundreds of kilometres in length. The extent of the assumed line source is estimated from the level and distribution of high-frequency peak acceleration amplitudes observed in a local seismic network. High-frequency motions are well suited for this approach, because they are mainly controlled by the distance to the rupturing fault. Observed ground-motion patterns are compared with theoretical templates modeled from empirical ground-motion prediction equations to determine the best line source and uncertainties. Our algorithm extends earlier work by Böse et al. for large finite-fault ruptures. This paper gives a detailed summary of the new algorithm and its offline performance for the 2016 M7.0 Kumamoto, Japan and 2014 M6.0 South Napa, California earthquakes, as well as its performance for about 100 real-time detected local earthquakes (2.2 ≤ M ≤ 5.1) in California. For most events, both the rupture length and the strike are well constrained within a few seconds (<10 s) of the event origin. In large earthquakes, this could allow for providing warnings of up to several tens of seconds. The algorithm could also be useful for resolving fault plane ambiguities of focal mechanisms and identification of rupturing faults for earthquakes as small as M2.5.

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Superficial simplicity of the 2010 El Mayor–Cucapah earthquake of Baja California in Mexico

Cited by 242 publications

References 25 publications

Application of Seismic Array Processing to Earthquake Early Warning

Application of Seismic Array Processing to Earthquake Early Warning

Pore pressure sensitivities to dynamic strains: Observations in active tectonic regions

FinDer v.2: Improved real-time ground-motion predictions for M2–M9 with seismic finite-source characterization

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