Improving Coseismic Slip Measurements

Abstract Postseismic Global Navigation Satellite System (GNSS) time series followed by megathrust earthquakes can be interpreted as a result of afterslip on the plate interface, especially in its early phase. Afterslip is a stress release process accumulated by adjacent coseismic slip and can be considered a recovery process for future events during earthquake cycles. Spatio-temporal evolution of afterslip often triggers subsequent earthquakes through stress perturbation. Therefore, it is important to quantitatively capture the spatio-temporal evolution of afterslip and related postseismic crustal deformation and to predict their future evolution with a physics-based simulation. We developed an adjoint data assimilation method, which directly assimilates GNSS time series into a physics-based model to optimize the frictional parameters that control the slip behavior on the fault. The developed method was validated with synthetic data. Through the optimization of frictional parameters, the spatial distributions of afterslip could roughly (but not in detail) be reproduced if the observation noise was included. The optimization of frictional parameters reproduced not only the postseismic displacements used for the assimilation, but also improved the prediction skill of the following time series. Then, we applied the developed method to the observed GNSS time series for the first 15 days following the 2003 Tokachi-oki earthquake. The frictional parameters in the afterslip regions were optimized to A–B ~ O(10 kPa), A ~ O(100 kPa), and L ~ O(10 mm). A large afterslip is inferred on the shallower side of the coseismic slip area. The optimized frictional parameters quantitatively predicted the postseismic GNSS time series for the following 15 days. These characteristics can also be detected if the simulation variables can be simultaneously optimized. The developed data assimilation method, which can be directly applied to GNSS time series following megathrust earthquakes, is an effective quantitative evaluation method for assessing risks of subsequent earthquakes and for monitoring the recovery process of megathrust earthquakes.

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Stimulus-range and magnitude estimates of distance based on object-size

Australian Journal of Psychology ◽

10.1080/00049536808255742 ◽

1968 ◽

Vol 20 (1) ◽

pp. 67-69 ◽

Cited By ~ 1

Author(s):

Gordon Stanley

Keyword(s):

Stimulus Range ◽

Object Size ◽

Magnitude Estimates

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Complex Slip Distribution of the 2021 Mw 7.4 Maduo, China, Earthquake: An Event Occurring on the Slowly Slipping Fault

Seismological Research Letters ◽

10.1785/0220210226 ◽

2021 ◽

Author(s):

Rumeng Guo ◽

Hongfeng Yang ◽

Yu Li ◽

Yong Zheng ◽

Lupeng Zhang

Keyword(s):

Slip Rate ◽

Slip Distribution ◽

Seismic Gap ◽

Seismogenic Fault ◽

Coseismic Slip ◽

Slip Rates ◽

Kunlun Mountain ◽

Coulomb Failure ◽

Main Fault ◽

Large Earthquakes

Abstract The 21 May 2021 Maduo earthquake occurred on the Kunlun Mountain Pass–Jiangcuo fault (KMPJF), a seismogenic fault with no documented large earthquakes. To probe its kinematics, we first estimate the slip rates of the KMPJF and Tuosuo Lake segment (TLS, ∼75 km north of the KMPJF) of the East Kunlun fault (EKLF) based on the secular Global Positioning System (GPS) data using the Markov chain Monte Carlo method. Our model reveals that the slip rates of the KMPJF and TLS are 1.7 ± 0.8 and 7.1 ± 0.3 mm/yr, respectively. Then, we invert high-resolution GPS and Interferometric Synthetic Aperture Radar observations to decipher the fault geometry and detailed coseismic slip distribution associated with the Maduo earthquake. The geometry of the KMPFJ significantly varies along strike, composed of five fault subsegments. The most slip is accommodated by two steeply dipping fault segments, with the patch of large sinistral slip concentrated in the shallow depth on a simple straight structure. The released seismic moment is ∼1.5×1020 N·m, equivalent to an Mw 7.39 event, with a peak slip of ∼9.3 m. Combining the average coseismic slip and slip rate of the main fault, an earthquake recurrence period of ∼1250−400+1120 yr is estimated. The Maduo earthquake reminds us to reevaluate the potential of seismic gaps where slip rates are low. Based on our calculated Coulomb failure stress, the Maduo earthquake imposes positive stress on the Maqin–Maqu segment of the EKLF, a long-recognized seismic gap, implying that it may accelerate the occurrence of the next major event in this region.

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An empirical study of New England seismicity: 1727-1977

Bulletin of the Seismological Society of America ◽

10.1785/bssa0690010159 ◽

1979 ◽

Vol 69 (1) ◽

pp. 159-175

Author(s):

R. Street ◽

A. Lacroix

Keyword(s):

Regression Analysis ◽

Empirical Study ◽

New England ◽

Multiple Regression Analysis ◽

Multiple Regression ◽

North American ◽

Isoseismal Map ◽

Epicentral Intensity ◽

Felt Area ◽

Magnitude Estimates

abstract Isoseismal map measurements and magnitudes of several recent central and northeastern North American earthquakes are related by multiple regression analysis in order that mbLg magnitudes can be estimated for those noninstrumentally-recorded New England events whose total felt area is known to be ≧10,000 km2 and which occurred after 1727. Magnitude estimates of the noninstrumentally-recorded events permit New England seismicity to be studied on a basis other than the heretofore conventional maximum epicentral intensity approach.

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Carbonaceous Materials in the Fault Zone of the Longmenshan Fault Belt: 1. Signatures within the Deep Wenchuan Earthquake Fault Zone and Their Implications

Minerals ◽

10.3390/min8090385 ◽

2018 ◽

Vol 8 (9) ◽

pp. 385 ◽

Cited By ~ 4

Author(s):

Li-Wei Kuo ◽

Jyh-Rou Huang ◽

Jiann-Neng Fang ◽

Jialiang Si ◽

Haibing Li ◽

...

Keyword(s):

Wenchuan Earthquake ◽

Fault Zone ◽

Active Fault ◽

Carbonaceous Materials ◽

Coseismic Slip ◽

Earthquake Fault ◽

Active Fault Zone ◽

2008 Wenchuan Earthquake ◽

Seismic Slip ◽

Longmenshan Fault

Graphitization of carbonaceous materials (CM) has been experimentally demonstrated as potential evidence of seismic slip within a fault gouge. The southern segment of the Longmenshan fault, a CM-rich-gouge fault, accommodated coseismic slip during the 2008 Mw 7.9 Wenchuan earthquake and potentially preserves a record of processes that occurred on the fault during the slip event. Here, we present a multi-technique characterization of CM within the active fault zone of the Longmenshan fault from the Wenchuan earthquake Fault Scientific Drilling-1. By contrast with field observations, graphite is pervasively and only distributed in the gouge zone, while heterogeneously crystallized CM are present in the surrounding breccia. The composite dataset that is presented, which includes the localized graphite layer along the 2008 Wenchuan earthquake principal slip zone, demonstrates that graphite is widely distributed within the active fault zone. The widespread occurrence of graphite, a seismic slip indicator, reveals that surface rupturing events commonly occur along the Longmenshan fault and are characteristic of this tectonically active region.

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Earthquake source parameters that display the first digit phenomenon

Nonlinear Processes in Geophysics ◽

10.5194/npg-22-625-2015 ◽

2015 ◽

Vol 22 (5) ◽

pp. 625-632

Author(s):

P. A. Toledo ◽

S. R. Riquelme ◽

J. A. Campos

Keyword(s):

Seismic Moment ◽

Waiting Times ◽

Source Parameters ◽

Tohoku Earthquake ◽

Earthquake Source ◽

Coseismic Slip ◽

Self Organized ◽

Earthquake Source Parameters ◽

Self Organized Criticality

Abstract. We study the main parameters of earthquakes from the perspective of the first digit phenomenon: the nonuniform probability of the lower first digit different from 0 compared to the higher ones. We found that source parameters like coseismic slip distributions at the fault and coseismic inland displacements show first digit anomaly. We also found the tsunami runups measured after the earthquake to display the phenomenon. Other parameters found to obey first digit anomaly are related to the aftershocks: we show that seismic moment liberation and seismic waiting times also display an anomaly. We explain this finding by invoking a self-organized criticality framework. We demonstrate that critically organized automata show the first digit signature and we interpret this as a possible explanation of the behavior of the studied parameters of the Tohoku earthquake.

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Multifault complex rupture and afterslip associated with the 2018 Mw 6.4 Hualien earthquake in northeastern Taiwan

Geophysical Journal International ◽

10.1093/gji/ggaa474 ◽

2020 ◽

Vol 224 (1) ◽

pp. 416-434

Author(s):

Dezheng Zhao ◽

Chunyan Qu ◽

Xinjian Shan ◽

Roland Bürgmann ◽

Wenyu Gong ◽

...

Keyword(s):

Main Shock ◽

Near Field ◽

Active Faults ◽

Fault Model ◽

Body Waves ◽

Coseismic Deformation ◽

Coseismic Slip ◽

Coulomb Stress Changes ◽

Seismic Displacement ◽

Stress Changes

SUMMARY We investigate the coseismic and post-seismic deformation due to the 6 February 2018 Mw 6.4 Hualien earthquake to gain improved insights into the fault geometries and complex regional tectonics in this structural transition zone. We generate coseismic deformation fields using ascending and descending Sentinel-1A/B InSAR data and GPS data. Analysis of the aftershocks and InSAR measurements reveal complex multifault rupture during this event. We compare two fault model joint inversions of SAR, GPS and teleseismic body waves data to illuminate the involved seismogenic faults, coseismic slip distributions and rupture processes. Our preferred fault model suggests that both well-known active faults, the dominantly left-lateral Milun and Lingding faults, and previously unrecognized oblique-reverse west-dipping and north-dipping detachment faults, ruptured during this event. The maximum slip of ∼1.6 m occurred on the Milun fault at a depth of ∼2–5 km. We compute post-seismic displacement time series using the persistent scatterer method. The post-seismic range-change fields reveal large surface displacements mainly in the near-field of the Milun fault. Kinematic inversions constrained by cumulative InSAR displacements along two tracks indicate that the afterslip occurred on the Milun and Lingding faults and the west-dipping fault just to the east. The maximum cumulative afterslip of 0.4–0.6 m occurred along the Milun fault within ∼7 months of the main shock. The main shock-induced static Coulomb stress changes may have played an important role in driving the afterslip adjacent to coseismic high-slip zones on the Milun, Lingding and west-dipping faults.

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