scholarly journals Slow Slip Events Following the 2002 Mw 7.1 Hualien Offshore Earthquake Afterslip

2021 ◽  
Author(s):  
Sean Kuanhsiang Chen ◽  
Yih-Min Wu ◽  
Yu-Chang Chan
Keyword(s):  
Coulomb Stress ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Slow Slip Event ◽  
Coulomb Stress Changes ◽  
Stress Changes ◽  
Slip Event ◽  
Slip Region ◽  
Recurrence Intervals ◽  
Offshore Earthquake

Abstract The recurrence intervals of slow slip events may increase gradually after a large earthquake during the afterslip. Stress perturbations during coseismic and postseismic periods may result in such an increase of intervals. However, the increasing recurrence intervals of slow slip events are rarely observed during an afterslip. The evolution process along with the afterslip remains unclear. We report an observation of slow slip events following the 2002 Mw 7.1 Hualien offshore earthquake afterslip in the southernmost Ryukyu subduction zone. Slow slip events in 2005, 2009, and 2015 are adjacent to the Mw 7.1 earthquake hypocenter. An increasing slow-slip interval of 3.1, 4.2, and 6.2 years has been observed after the earthquake. We calculated coseismic and postseismic slips from the Mw 7.1 earthquake and then estimated the Coulomb stress changes in the slow slip region. The Mw 7.1 earthquake has contributed positive Coulomb stresses to both the 2005 slow-slip region and 2009/2015 repeating slow-slip region. The coseismic and postseismic Coulomb stress change on the 2005 slow-slip region is approximately 0.05 MPa and 0.035 MPa, respectively. However, both Coulomb stress changes on the 2009/2015 repeating slow-slip region are not over 0.03 MPa. The ongoing afterslip following the Mw 7.1 earthquake last for at least five years, evolving with a decaying stress rate with time. The long-term stress perturbations may be able to trigger the 2005 slow slip event during the afterslip. The 2009 slow slip event seems to be influenced by the afterslip as well. Postseismic stress evolution and frictional and stressed conditions of the slow-slip region can be a reason to affect the evolution process of slow slip events intervals.

Observing seismic signatures of slow slip events with unsupervised learning

2021 ◽  
Author(s):  
Leonard Seydoux ◽  
Michel Campillo ◽  
René Steinmann ◽  
Randall Balestriero ◽  
Maarten de Hoop
Keyword(s):  
Clustering Algorithm ◽  
Low Frequency ◽  
Seismic Signal ◽  
Geodetic Data ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Slow Slip Event ◽  
Intermittent Behavior ◽  
Slow Earthquakes ◽  
Slip Event

<p>Slow slip events are observed in geodetic data, and are occasionally associated with seismic signatures such as slow earthquakes (low-frequency earthquakes, tectonic tremors). In particular, it was shown that swarms of slow earthquake can correlate with slow slip events occurrence, and allowed to reveal the intermittent behavior of several slow slip events. This observation was possible thanks to detailed analysis of slow earthquakes catalogs and continuous geodetic data, but in every case, was limited to particular classes of seismic signatures. In the present study, we propose to infer the classes of seismic signals that best correlate with the observed geodetic data, including the slow slip event. We use a scattering network (a neural network with wavelet filters) in order to find meaningful signal features, and apply a hierarchical clustering algorithm in order to infer classes of seismic signal. We then apply a regression algorithm in order to predict the geodetic data, including slow slip events, from the occurrence of inferred seismic classes. This allow to (1) identify seismic signatures associated with the slow slip events as well as (2) infer the the contribution of each classes to the overall displacement observed in the geodetic data. We illustrate our strategy by revisiting the slow-slip event of 2006 that occurred beneath Guerrero, Mexico.</p>

AutoCoulomb: An Automated Configurable Program to Calculate Coulomb Stress Changes on Receiver Faults with Any Orientation and its Application to the 2020 Mw 7.8 Simeonof Island, Alaska, Earthquake

2021 ◽  
Author(s):  
Jianjun Wang ◽  
Caijun Xu ◽  
Jeffrey T. Freymueller ◽  
Yangmao Wen ◽  
Zhuohui Xiao
Keyword(s):  
Batch Process ◽  
Stress Change ◽  
Coulomb Stress ◽  
Slow Slip ◽  
Coulomb Stress Change ◽  
Coulomb Stress Changes ◽  
Stress Changes ◽  
Command Line Tool ◽  
Alaska Earthquake

Abstract Coulomb stress change is the change in resultant force of shear stress and friction imposed on a receiver fault plane. The resulting stress change is often computed using the Coulomb 3.4 and the postseismic Green’s functions and postseismic components (PSGRN-PSCMP) programs. Notwithstanding both preferences, both have incomplete optimally oriented failure planes (OOPs) and are inconvenient to resolve Coulomb stress changes on various fault planes placed in varying depths. Here, we present an alternative program termed AutoCoulomb. It leverages the shell command-line tool to automatically batch-process Coulomb stress changes on all sorts of receiver fault planes. We first validate the program. We then apply it to the 2020 Mw 7.8 Simeonof Island, Alaska, earthquake, as a case study. Our results show that Coulomb stress changes resolved on fixed receiver faults, using the three programs, are in line with each other. So are those resolved on 3D OOPs using the PSGRN–PSCMP and the AutoCoulomb programs. Nevertheless, Coulomb stress changes on 2D OOPs, generated by the AutoCoulomb program, always outweigh those done by the Coulomb 3.4 program, indicating that 2D OOPs constrained by the latter are not the most optimal. Some nonoptimal 2D OOPs result in the reversal of the signs of Coulomb stress changes, posing a risk of misleading stress shadows with negative Coulomb stress changes. For the case study, the 28 July 2020 Mw 6.1 aftershock received a positive coseismic Coulomb stress change of ∼3.5 bars. In contrast, the compounded coseismic Coulomb stress changes at the hypocenters of the 1946 Mw 8.2, the 1948 Mw 7.2, and the 2020 Mw 7.8 earthquakes are within a range from −1.1 to 0.1 bar, suggesting that coseismic Coulomb stress changes promoted by preceding mainshocks alone are not responsible for these mainshocks. Other factors, such as postseismic viscoelastic relaxation, afterslip, and slow slip, may contribute to promoting their occurrence.

scholarly journals Earthquake triggering model based on normal-stress-dependent Nagata law: application to the 2016 Mie offshore earthquake

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Shingo Yoshida ◽  
Takuto Maeda ◽  
Naoyuki Kato
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Static Stress ◽  
Stress Dependence ◽  
Slow Slip ◽  
Earthquake Triggering ◽  
Slow Slip Events ◽  
Stress Changes ◽  
Stress Dependent ◽  
Offshore Earthquake

Abstract We propose a normal-stress-dependent Nagata law. Nagata et al. (J Geophys Res 117:B02314, 2012) revised the rate- and state-dependent friction law by introducing the shear stress dependence. We further extended the Nagata law by incorporating the normal stress dependence obtained by Linker and Dieterich (J Geophys Res 97:4923–4940, 1992). We performed numerical simulations of earthquake triggering by assuming the extended Nagata law. In the case of repeated earthquakes, we applied dynamic Coulomb failure function (CFF) perturbation due to normal or shear stress changes. CFF perturbation increased the slip velocity after the cessation of perturbation, relative to that of the repeated events without triggering. This leads to dynamic earthquake triggering for certain perturbation amplitudes with time to instability of 0 to several tens of days. In addition, triggering potential of the static CFF jump (ΔCFFs) was investigated. Static stress perturbation has a higher triggering potential than dynamic stress perturbation for the same magnitude of CFF. The equivalent ΔCFFeq is evaluated for dynamic perturbation that results in a triggering potential approximately the same as in the case of static stress perturbation if ΔCFFs = ΔCFFeq. We calculated ΔCFFeq on the interface of the Philippine Sea plate for the Mie offshore earthquake, which occurred around the Nankai Trough on April 1, 2016, using OpenSWPC. The results shows that ΔCFFeq is large around the trough, where slow slip events followed the Mie earthquake, suggesting that a large ΔCFFeq may have triggered slow slip events.

scholarly journals Slip bursts during coalescence of slow slip events in Cascadia

2021 ◽  
Author(s):  
Quentin Bletery ◽  
Jean-Mathieu Nocquet
Keyword(s):  
Laboratory Experiments ◽  
Experimental Studies ◽  
Slow Slip ◽  
Ground Displacement ◽  
Gps Measurements ◽  
Dynamic Simulations ◽  
Slow Slip Events ◽  
Slow Slip Event ◽  
Slip Event ◽  
Continuous Gps

<p>Both laboratory experiments and dynamic simulations suggest that earthquakes can be preceded by a precursory phase of slow slip. Observing processes leading to an acceleration or spreading of slow slip along faults is therefore key to understand the dynamics potentially leading to seismic ruptures. Here, we use continuous GPS measurements of the ground displacement to image the daily slip along the fault beneath Vancouver Island during a slow slip event in 2013. We image the coalescence of three originally distinct slow slip fronts merging together. We show that during coalescence phases lasting for 2 to 5 days, the rate of energy (moment) release significantly increases. This observation supports the view proposed by theoretical and experimental studies that the coalescence of slow slip fronts is a possible mechanism for initiating earthquakes.</p>

scholarly journals Adjoint Slip Inversion under a Constrained Optimization Framework: Revisiting the 2006 Guerrero Slow Slip Event

2020 ◽  
Author(s):  
Josué Tago ◽  
Víctor M. Cruz-Atienza ◽  
Carlos Villafuerte ◽  
Takuya Nishimura ◽  
Vladimir Kostoglodov ◽  
...  
Keyword(s):  
Constrained Optimization ◽  
Slow Slip ◽  
Slow Slip Event ◽  
Optimization Framework ◽  
Slip Event

scholarly journals ANALYSING POST-SEISMIC DEFORMATION OF IZMIT EARTHQUAKE WITH INSAR, GNSS AND COULOMB STRESS MODELLING

2016 ◽  
Vol XLI-B1 ◽  
pp. 417-421 ◽  
Author(s):  
R. Alac Barut ◽  
J. Trinder ◽  
C. Rizos
Keyword(s):  
Measurement Techniques ◽  
Satellite System ◽  
Northern Region ◽  
Strike Slip ◽  
Coulomb Stress ◽  
North West ◽  
Coulomb Stress Changes ◽  
Izmit Earthquake ◽  
The North ◽  
Stress Changes

On August 17<sup>th</sup> 1999, a M<sub>w</sub> 7.4 earthquake struck the city of Izmit in the north-west of Turkey. This event was one of the most devastating earthquakes of the twentieth century. The epicentre of the Izmit earthquake was on the North Anatolian Fault (NAF) which is one of the most active right-lateral strike-slip faults on earth. However, this earthquake offers an opportunity to study how strain is accommodated in an inter-segment region of a large strike slip fault. In order to determine the Izmit earthquake post-seismic effects, the authors modelled Coulomb stress changes of the aftershocks, as well as using the deformation measurement techniques of Interferometric Synthetic Aperture Radar (InSAR) and Global Navigation Satellite System (GNSS). The authors have shown that InSAR and GNSS observations over a time period of three months after the earthquake combined with Coulomb Stress Change Modelling can explain the fault zone expansion, as well as the deformation of the northern region of the NAF. It was also found that there is a strong agreement between the InSAR and GNSS results for the post-seismic phases of investigation, with differences less than 2mm, and the standard deviation of the differences is less than 1mm.

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