Finite Slip Models of the 2019 Ridgecrest Earthquake Sequence Constrained by Space Geodetic Data and Aftershock Locations

2020 ◽  
Vol 110 (4) ◽  
pp. 1660-1679 ◽  
Author(s):  
Zeyu Jin ◽  
Yuri Fialko
Keyword(s):  
Stress Transfer ◽  
Nucleation Site ◽  
Strike Slip ◽  
Earthquake Sequence ◽  
Slip Distribution ◽  
Depth Interval ◽  
Coseismic Slip ◽  
Moderate Amount ◽  
Coulomb Stress Changes ◽  
Stress Changes

ABSTRACT The July 2019 Ridgecrest, California, earthquake sequence involved two large events—the M 6.4 foreshock and the M 7.1 mainshock that ruptured a system of intersecting strike-slip faults. We present analysis of space geodetic observations including Synthetic Aperture Radar and Global Navigation Satellite System data, geological field mapping, and seismicity to constrain the subsurface rupture geometry and slip distribution. The data render a complex pattern of faulting with a number of subparallel as well as cross-cutting fault strands that exhibit variations in both strike and dip angles, including a “flower structure” formed by shallow splay faults. Slip inversions are performed using both homogeneous and layered elastic half-space models informed by the local seismic tomography data. The inferred slip distribution suggests a moderate amount of the shallow coseismic slip deficit. The peak moment release occurred in the depth interval of 3–4 km, consistent with results from previous studies of major strike-slip earthquakes, and the depth distribution of seismicity in California. We use the derived slip models to investigate stress transfer and possible triggering relationships between the M 7.1 mainshock and the M 6.4 foreshock, as well as other moderate events that occurred in the vicinity of the M 7.1 hypocenter. Triggering is discouraged for the average strike of the M 7.1 rupture (320°) but encouraged for the initial orientation of the mainshock rupture suggested by the first-motion data (340°). This lends support to a scenario according to which the earthquake rupture nucleated on a small fault that was more optimally oriented with respect to the regional stress and subsequently propagated along the less-favorably oriented pre-existing faults, possibly facilitated by dynamic weakening. The nucleation site of the mainshock experienced positive dynamic Coulomb stress changes that are much larger than the static stress changes, yet the former failed to initiate rupture.

Tectonic Context and Possible Triggering of the 2019–2020 Puerto Rico Earthquake Sequence

2022 ◽  
Author(s):  
Marjolein Blasweiler ◽  
Matthew W. Herman ◽  
Fenna Houtsma ◽  
Rob Govers
Keyword(s):  
Puerto Rico ◽  
Fault Zone ◽  
Plate Boundary ◽  
Strike Slip ◽  
Global Navigation Satellite Systems ◽  
Earthquake Sequence ◽  
Motion Direction ◽  
Lateral Strike Slip ◽  
Coulomb Stress Changes ◽  
Stress Changes

Abstract An historically unprecedented seismic moment was released by crustal events of the 2019–2020 earthquake sequence near southwest Puerto Rico. The sequence involved at least two, and perhaps three interacting fault systems. The largest Mw 6.4 event was likely triggered by left lateral strike-slip events along the eastern extension of the North Boquerón Bay-Punta Montalva fault zone. The mainshock occurred in a normal fault zone that extends into a region where previous studies documented extensional deformation, beyond the Ponce fault and the Bajo Tasmanian fault. Coulomb stress changes by the mainshock may have triggered further normal-faulting aftershocks, left lateral strike-slip events in the region where these two fault zones interacted, and possibly right lateral strike-slip aftershocks along a third structure extending southward, the Guayanilla fault zone. Extension directions of the seismic sequence are consistently north-northwest–south-southeast-oriented, in agreement with the Global Navigation Satellite Systems-inferred motion direction of eastern Hispaniola relative to western Puerto Rico, and with crustal stress estimates for the overriding plate boundary zone.

scholarly journals Surface Rupture Kinematics and Coseismic Slip Distribution during the 2019 Mw7.1 Ridgecrest, California Earthquake Sequence Revealed by SAR and Optical Images

2020 ◽  
Vol 12 (23) ◽  
pp. 3883
Author(s):  
Chenglong Li ◽  
Guohong Zhang ◽  
Xinjian Shan ◽  
Dezheng Zhao ◽  
Yanchuan Li ◽  
...  
Keyword(s):  
Strike Slip ◽  
Earthquake Sequence ◽  
Slip Distribution ◽  
Fault System ◽  
Seismogenic Fault ◽  
Coseismic Slip ◽  
Surface Rupture ◽  
Lateral Strike Slip ◽  
Optical Images ◽  
Rupture Kinematics

The 2019 Ridgecrest, California earthquake sequence ruptured along a complex fault system and triggered seismic and aseismic slips on intersecting faults. To characterize the surface rupture kinematics and fault slip distribution, we used optical images and Interferometric Synthetic Aperture Radar (InSAR) observations to reconstruct the displacement caused by the earthquake sequence. We further calculated curl and divergence from the north-south and east-west components, to effectively identify the surface rupture traces. The results show that the major seismogenic fault had a length of ~55 km and strike of 320° and consisted of five secondary faults. On the basis of the determined multiple-fault geometries, we inverted the coseismic slip distributions by InSAR measurements, which indicates that the Mw7.1 mainshock was dominated by the right-lateral strike-slip (maximum strike-slip of ~5.8 m at the depth of ~7.5 km), with a small dip-slip component (peaking at ~1.8 m) on an east-dipping fault. The Mw6.4 foreshock was dominated by the left-lateral strike-slip on a north-dipping fault. These earthquakes triggered obvious aseismic creep along the Garlock fault (117.3° W–117.5° W). These results are consistent with the rupture process of the earthquake sequence, which featured a complicated cascading rupture rather than a single continuous rupture front propagating along multiple faults.

Seismic doublets and a complex seismic sequence controlled by the rotation of the Juan Fernández microplate

2021 ◽  
Author(s):  
Simone Cesca ◽  
Carla Valenzuela Malebrán ◽  
José Ángel López-Comino ◽  
Timothy Davis ◽  
Carlos Tassara ◽  
...  
Keyword(s):  
Source Parameters ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Joint Analysis ◽  
Seismic Sequence ◽  
Local Data ◽  
Study Region ◽  
Coulomb Stress Changes ◽  
Earthquake Source Parameters ◽  
Stress Changes

<p> A complex seismic sequence took place in 2014 at the Juan Fernández microplate, a small microplate located between Pacific, Nazca and Antarctica plates. Despite the remoteness of the study region and the lack of local data, we were able to resolve earthquake source parameters and to reconstruct the complex seismic sequence, by using modern waveform-based seismological techniques. The sequence started with an exceptional Mw 7.1-6.7 thrust – strike slip earthquake doublet, the first subevent being the largest earthquake ever recorded in the region and one of the few rare thrust earthquakes in a region otherwise characterized by normal faulting and strike slip earthquakes. The joint analysis of seismicity and focal mechanisms suggest the activation of E-W and NE-SW faults or of an internal curved pseudofault, which is formed in response to the microplate rotation, with alternation of thrust and strike-slip earthquakes. Seismicity migrated Northward in its final phase, towards the microplate edge, where a second doublet with uneven focal mechanisms occurred. The sequence rupture kinematics is well explained by Coulomb stress changes imparted by the first subevent. Our analysis show that compressional stresses, which have been mapped at the northern boundary of the microplate, but never accompanied by large thrust earthquakes, can be accommodated by the rare occurrence of large, impulsive, shallow thrust earthquakes, with a considerable tsunamigenic potential.</p>

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

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.

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.

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.

The delayed aftershocks of the Illapel Earthquake Mw 8.3, 2015, Chile

2021 ◽  
Author(s):  
Franco Lema ◽  
Mahesh Shrivastava
Keyword(s):  
Tide Gauge ◽  
Stress Transfer ◽  
Large Earthquake ◽  
Seismic Source ◽  
Coulomb Stress ◽  
Coulomb Stress Changes ◽  
Finite Fault ◽  
Stress Changes ◽  
2015 Illapel Earthquake ◽  
Illapel Earthquake

&lt;p&gt;The delayed aftershocks 2018 Mw 6.2 on April 10 and Mw 5.8 on Sept 1 and 2019 Mw 6.7 on January 20, Mw 6.4 on June 14, and Mw 6.2 on November 4, associated with the Mw 8.3 2015 Illapel Earthquake occurred in the &amp;#8203;&amp;#8203;central Chile. The seismic source of this earthquake has been studied with the GPS, InSAR and tide gauge network. Although there are several studies performed to characterize the robust aftershocks and the variations in the field of deformation induced by the megathrust, but there are still aspects to be elucidated of the relationship between the transfer of stresses from the interface between plates towards delayed aftershocks with the crustal structures with seismogenic potential. Therefore, the principal objective of this study is to understand how the stress transfer induced by the 2015 Illapel earthquake of the heterogeneous rupture mechanism to intermediate-deep or crustal earthquakes. For this, coulomb stress changes from &amp;#160;finite fault model of the Illapel earthquake and with the biggest aftershocks in year 2015 are used. These cumulative stress pattern provides substantial evidences for the delayed aftershocks in this region. The subducting Challenger Fault Zone and Juan Fernandez Ridge heterogeneity are existing feature, which releases the accumulated coulomb stress changes and provide delayed aftershocks.&amp;#160; Therefore along with stress induced by a large earthquake such as Mw 8.3 from Illapel 2015 along with biggest aftershocks, have a direct mechanism that may activate the&amp;#160; delayed aftershocks. Our study suggests &amp;#160;the activation of crustal faults in this research as a risk assessment factor for the evaluating in the seismic context of the region and useful for another subduction zone.&lt;/p&gt;

scholarly journals Static stress transfer from the May 20, 2012, M 6.1 Emilia-Romagna (northern Italy) earthquake using a co-seismic slip distribution model

2012 ◽  
Vol 55 (4) ◽  
Author(s):  
Athanassios Ganas ◽  
Zafeiria Roumelioti ◽  
Konstantinos Chousianitis
Keyword(s):  
Stress Transfer ◽  
Northern Italy ◽  
Static Stress ◽  
Distribution Model ◽  
Coulomb Stress ◽  
Coulomb Stress Changes ◽  
Seismic Slip ◽  
Seismological Data ◽  
Stress Changes ◽  
Fixed Orientation

<p>We model the static stress transfer for the May 2012 northern Italy earthquakes, assuming that failure of the crust occurs by shear. This allows the mechanics of the process to be approximated by the Okada (1992) expressions for displacement and strain fields due to a finite rectangular source in an elastic, homogeneous and isotropic half-space. The slip model of the May 20, 2012, earthquake was derived using empirical Green’s functions and a least-squares inversion scheme of source time functions computed from regional broadband seismological data. The derived model is then incorporated into the computation of Coulomb stress change (ΔCFF) to investigate the possibility that the May 20, 2012, M 6.1 event triggered the second earthquake that occurred on May 29, 2012 (M 5.9). We calculate the Coulomb stress changes for both: (a) optimally oriented planes to regional compression; and (b) planes of fixed orientation assuming that E-W striking, south-dipping thrust faults of the May 29, 2012, type of rupture was a candidate for failure. In both cases, we find that the triggering is promoted as the ΔCFF values in the hypocentral area of the May 29, 2012, earthquake are positive (between 0.61-0.74 bar).</p><p> </p>

scholarly journals Coseismic stress distribution along active structures and their influence on timedependent probability values.

2016 ◽  
Vol 47 (3) ◽  
pp. 1211
Author(s):  
P. Paradisopoulou ◽  
E. Papadimitriou ◽  
J. Mirek ◽  
V. Karakostas
Keyword(s):  
Occurrence Rate ◽  
Recurrence Time ◽  
Time Interval ◽  
Coseismic Slip ◽  
Coulomb Stress Changes ◽  
Earthquake Probability ◽  
Fault Segment ◽  
Active Structures ◽  
Probability Estimates ◽  
Stress Changes

Based on the fact that stress changes caused by the coseismic slip of strong events can be incorporated into quantitative earthquake probability estimates, the goal of this study is to estimate the probability of the next strong earthquake (M≥6.5) on a known fault segment in a future time interval (30 years). The probability depends on the calculation of ΔCFF and the estimate of the occurrence rate of a characteristic earthquake, conditioned to the elapsed time since the previous event. The Coulomb stress changes caused by previous earthquakes are computed and their influence are considered by the introduction of a permanent shift on the time elapsed since theprevious earthquake or by a modification of the expected mean recurrence time. The occurrence rate is calculated, taking into account both permanent and temporary perturbations. The estimated probability values correspond to the probabilities along each fault segment with discretization of 1km, illustrating the probability distribution across the specific fault. In order to check whether the estimated probability vary with depth, all the estimations were performed for each fault at depths of 8, 10, 12 and 15 km. 

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