The Potential of Using Dynamic Strains in Earthquake Early Warning Applications

Farghal, Noha S.; Barbour, Andrew J.; Langbein, John

doi:10.1785/0220190385

Cited by 7 publications

(2 citation statements)

References 26 publications

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“…They aim to provide a time-window to act before strong shaking happens to help alleviate damages and injuries. Well-functioning systems strongly rely on fast and robust estimates of earthquake magnitudes, source locations and ground motions [82]. As a major component of EEW networks, both seismometers and high-rate GNSS sensors may however show limitations in recording near-source large ground motions with high-resolution [83,84].…”

Section: Rapid Moment Magnitude Estimate and Implications For Eew Sys...mentioning

confidence: 99%

“…As a major component of EEW networks, both seismometers and high-rate GNSS sensors may however show limitations in recording near-source large ground motions with high-resolution [83,84]. Strainmeters have the capability to record the whole spectrum of elastodynamic deformation (static and dynamic) [34] with little noise level, without saturation, and with no additional signal processing, and therefore show potential for EEW applications [82]. An earthquake magnitude scale based on local broadband dynamic strain waveforms has recently been developed by Barbour et al (2021) [85].…”

Section: Rapid Moment Magnitude Estimate and Implications For Eew Sys...mentioning

confidence: 99%

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Fifteen Years of Continuous High-Resolution Borehole Strainmeter Measurements in Eastern Taiwan: An Overview and Perspectives

et al. 2021

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As one of the most sensitive instruments for deformation monitoring in geophysics, borehole strainmeter has the capability to record a large spectrum of tectonic and environmental signals. Sensors are usually deployed near active faults and volcanoes and provide high-resolution continuous recordings of seismic and aseismic signals, hydrological variations (rainfall, groundwater level) and natural hazards (tropical cyclones, landslides, tsunamis). On the occasion of the 50th anniversary of the installation of the first Sacks–Evertson borehole strainmeter, in central Japan, we present an overview of the major scientific contributions and advances enabled by borehole strainmeter measurements in Taiwan since their installation in the mid 2000s. We also propose a set of future research directions that address recent challenges in seismology, hydrology and crustal strain modeling.

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Section: Rapid Moment Magnitude Estimate and Implications For Eew Sys...mentioning

confidence: 99%

Section: Rapid Moment Magnitude Estimate and Implications For Eew Sys...mentioning

confidence: 99%

Fifteen Years of Continuous High-Resolution Borehole Strainmeter Measurements in Eastern Taiwan: An Overview and Perspectives

et al. 2021

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Optimizing Earthquake Early Warning Alert Distance Strategies Using the July 2019 Mw 6.4 and Mw 7.1 Ridgecrest, California, Earthquakes

Saunders

Aagaard

Baltay

et al. 2020

Bulletin of the Seismological Society of America

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ABSTRACT The ShakeAlert earthquake early warning system aims to alert people who experience modified Mercalli intensity (MMI) IV+ shaking during an earthquake using source estimates (magnitude and location) to estimate median-expected peak ground motions with distance, then using these ground motions to determine median-expected MMI and thus the extent of MMI IV shaking. Because median ground motions are used, even if magnitude and location are correct, there will be people outside the alert region who experience MMI IV shaking but do not receive an alert (missed alerts). We use 91,000 “Did You Feel It?” survey responses to the July 2019 Mw 6.4 and Mw 7.1 Ridgecrest, California, earthquakes to determine which ground-motion to intensity conversion equation (GMICE) best fits median MMI with distance. We then explore how incorporating uncertainty from the ground-motion prediction equation and the GMICE in the alert distance calculation can produce more accurate MMI IV alert regions for a desired alerting strategy (e.g., aiming to alert 95% of people who experience MMI IV+ shaking), assuming accurate source characterization. Without incorporating ground-motion uncertainties, we find MMI IV alert regions using median-expected ground motions alert fewer than 20% of the population that experiences MMI IV+ shaking. In contrast, we find >94% of the people who experience MMI IV+ shaking can be included in the MMI IV alert region when two standard deviations of ground-motion uncertainty are included in the alert distance computation. The optimal alerting strategy depends on the false alert tolerance of the community due to the trade-off between minimizing missed and false alerts. This is especially the case for situations like the Mw 6.4 earthquake when alerting 95% of the 5 million people who experience MMI IV+ also results in alerting 14 million people who experience shaking below this level and do not need to take protective action.

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Strain-Estimated Ground Motions Associated with Recent Earthquakes in California

Farghal

Baltay

Langbein

2020

Bulletin of the Seismological Society of America

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Peak ground velocity (PGV) is a commonly used parameter in earthquake ground-motion models (GMMs) and hazard analyses, because it is closely related to structural damage and felt ground shaking, and is typically measured on broadband seismometers. Here, we demonstrate that strainmeters, which directly measure in situ strain in the bulk rock, can easily be related to ground velocity by a factor of bulk shear-wave velocity and, thus, can be used to measure strain-estimated PGV. We demonstrate the parity of velocity to strain utilizing data from borehole strainmeters deployed along the plate boundaries of the west coast of the United States for nine recent M 4.4–7.1 earthquakes in California, including the largest two events of the July 2019 Ridgecrest earthquake sequence. PGVs derived from maximum horizontal shear strains fall within the range of seismic-estimated values recorded at the same distances. We compare the strain-estimated data with GMMs based on seismic PGVs and find consistency in residual polarity (positive vs. negative; the sign of the difference between observed and modeled data) for certain earthquake–station paths, where some paths indicate an overestimation and others indicate an underestimation of strain-derived PGVs, as compared with the GMMs. We surmise that this may be indicative of over or underestimation of shear-wave velocity along those paths, as compared with the average velocity used to derive PGV from strain measurements, or indicative of repeatable site and path effects that are not accounted for in our analyses. This direct comparison of strain with velocity can highlight physical path effects, as well as improve the density and capability of ground-motion recordings.

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The Potential of Using Dynamic Strains in Earthquake Early Warning Applications

Cited by 7 publications

References 26 publications

Fifteen Years of Continuous High-Resolution Borehole Strainmeter Measurements in Eastern Taiwan: An Overview and Perspectives

Fifteen Years of Continuous High-Resolution Borehole Strainmeter Measurements in Eastern Taiwan: An Overview and Perspectives

Optimizing Earthquake Early Warning Alert Distance Strategies Using the July 2019 Mw 6.4 and Mw 7.1 Ridgecrest, California, Earthquakes

Strain-Estimated Ground Motions Associated with Recent Earthquakes in California

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