Reviving<i>m</i>B

Kanamori, Hiroo; Ross, Zachary E.

doi:10.1093/gji/ggy510

Cited by 17 publications

(23 citation statements)

References 58 publications

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“…These are similar to the average value for large interplate thrust events (e.g., Ye et al, 2016) and lower than typical values (~4.0 × 10 −5 ) for large strike-slip events (e.g., Ye et al, 2015). Measurements of m B for periods of~3.5 s (Kanamori & Ross, 2018) are 6.08 (foreshock) and 6.71 (mainshock), predicting relatively low values of scaled radiated energy; E R_B /M 0 = 0.5 × 10 −5 (foreshock) and 1.4 × 10 −5 (mainshock; H. Kanamori, personal communication, 2 August 2019).…”

Section: Discussionmentioning

confidence: 99%

Coseismic Rupture Process of the Large 2019 Ridgecrest Earthquakes From Joint Inversion of Geodetic and Seismological Observations

Liu

Lay

Brodsky

et al. 2019

Geophysical Research Letters

118

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On 4 and 6 July 2019, two large strike‐slip earthquakes with W‐phase moment magnitudes MWW 6.5 (foreshock) and MWW 7.1 (mainshock) struck the Eastern California Shear Zone, northeast of Ridgecrest. The faulting geometry and kinematic coseismic slip distribution of both events are determined by jointly inverting seismological and geodetic observations guided by aftershock and surface rupture locations. The foreshock ruptured two orthogonal faults with a prominent L‐shaped geometry with maximum slip of ~1.1 m on the NE‐SW segment. The mainshock faulting extended NW‐SE along several primary fault segments that straddle the foreshock slip. The surface rupture and slip model indicate mostly near‐horizontal strike‐slip motion with maximum slip of ~3.7 m, but there is a localized vertical dip‐slip motion. Both the foreshock and mainshock ruptures terminate in regions of complex surface offsets. High aftershock productivity and low rupture velocity may be the result of rupture of a relatively immature fault system.

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Section: Discussionmentioning

confidence: 99%

Coseismic Rupture Process of the Large 2019 Ridgecrest Earthquakes From Joint Inversion of Geodetic and Seismological Observations

Liu

Lay

Brodsky

et al. 2019

Geophysical Research Letters

118

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“…In this study, we seek a simple seismic waveform proxy for occurrence of shallow coseismic slip on the megathrust. This can supplement information from rapid focal mechanism determination by methods such as W phase inversion (Kanamori & Rivera, 2008) and various energy and magnitude methods for detecting the specific subclass of shallow rupturing tsunami earthquakes (e.g., Kanamori & Ross, 2018;Newman & Okal, 1998). Ward (1979) observed pronounced P coda "ringing" in the interval between the direct P and PP waves on teleseismic vertical component seismograms for large oceanic earthquakes.…”

Section: 1029/2019gl082774mentioning

confidence: 99%

Evaluating the Updip Extent of Large Megathrust Ruptures Using P_coda Levels

Lay

Rhode

2019

Geophysical Research Letters

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When slip at shallow depth occurs during large subduction zone thrust events, P wave energy enters the water layer and establishes pwP, the reverberating waves called “water bounces” that follow pP. For water depths ≥5–6 km (i.e., near the trench) above the shallow slip, pwP manifests in a strong ~10‐s period ringing that can persist for minutes into the teleseismic P wave coda at all azimuths. Deeper slip can generate shorter‐period pwP ringing at trenchward azimuths. At large distances, Pcoda windows have several‐minute‐long intervals free of secondary arrivals. We consider rmsPcoda/rmsP amplitude ratios at distances from 80° to 120° as a potential proxy for occurrence of shallow slip for 39 MW 7.5+ megathrust earthquakes from 1990 to 2016 with estimated slip distributions. Ratios for the 15‐ to 7‐s‐period band have a strong bimodal distribution, with higher average Pcoda/P amplitudes observed for ruptures with slip extending to shallow depth.

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“…The time is UTC and the unit of energy is joule. m B is the body-wave magnitude computed with the method by Kanamori & Ross (2019). Since the synthetic seismograms are computed for a given moment-rate function and mechanism, we can estimate the radiated energy at the hypocentre.…”

mentioning

confidence: 99%

Estimation of radiated energy using the KiK-net downhole records—old method for modern data

Kanamori

Ross

Rivera

2020

Geophysical Journal International

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SUMMARY We use KiK-net (NIED) downhole records to estimate the radiated energy, ER, of 29 Japanese inland earthquakes with a magnitude range from Mw = 5.6 to 7.0. The method is based on the work of Gutenberg and Richter in which the time integral of S-wave ground-motion velocity-squared is measured as a basic metric of the radiated energy. Only stations within a distance of 100 km are used to minimize complex path and attenuation effects. Unlike the teleseismic method that uses mainly P waves, the use of S waves which carry more than 95 per cent of the radiated energy allows us to obtain robust results. We calibrate the method using synthetic seismograms to modernize and improve the Gutenberg–Richter method. We compute synthetic seismograms for a source model of each event with a given source function (i.e. known ER), the actual mechanism and the source-station geometry. Then, we compare the given ER with the computed energy metric to correct for the unknown effect of wave propagation and the mechanism. The use of downhole records minimizes the uncertainty resulting from the site response. Our results suggest that the currently available estimates of ER from teleseismic data are probably within a factor of 3, on average, of the absolute value. The scaled energy eR ( = ER/M0) is nearly constant at about 3 × 10−5 over a magnitude range from Mw = 5.6 to 7.0 with a slight increasing trend with Mw. We found no significant difference in eR between dip-slip and strike-slip events.

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RevivingmB

Cited by 17 publications

References 58 publications

Coseismic Rupture Process of the Large 2019 Ridgecrest Earthquakes From Joint Inversion of Geodetic and Seismological Observations

Coseismic Rupture Process of the Large 2019 Ridgecrest Earthquakes From Joint Inversion of Geodetic and Seismological Observations

Evaluating the Updip Extent of Large Megathrust Ruptures Using P_coda Levels

Estimation of radiated energy using the KiK-net downhole records—old method for modern data

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RevivingmB

Cited by 17 publications

References 58 publications

Coseismic Rupture Process of the Large 2019 Ridgecrest Earthquakes From Joint Inversion of Geodetic and Seismological Observations

Coseismic Rupture Process of the Large 2019 Ridgecrest Earthquakes From Joint Inversion of Geodetic and Seismological Observations

Evaluating the Updip Extent of Large Megathrust Ruptures Using Pcoda Levels

Estimation of radiated energy using the KiK-net downhole records—old method for modern data

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Evaluating the Updip Extent of Large Megathrust Ruptures Using P_coda Levels