scholarly journals The March 2021 Tyrnavos, central Greece, doublet (Μw6.3 and Mw6.0): Aftershock relocation, faulting details, coseismic slip and deformation

2021 ◽  
Vol 58 ◽  
pp. 131
Author(s):  
Vasileios Karakostas ◽  
Costas Papazachos ◽  
Eleftheria Papadimitriou ◽  
Michael Foumelis ◽  
Anastasia Kiratzi ◽  
...  
Keyword(s):  
Main Shock ◽  
Small Towns ◽  
Local Network ◽  
Coseismic Slip ◽  
Waveform Data ◽  
Coulomb Stress Changes ◽  
Rupture Length ◽  
Finite Fault ◽  
Main Shocks ◽  
Stress Changes

On 3 March 2021, the Mw6.3 Tyrnavos earthquake shook much of the Thessalia region, leading to extensive damage in many small towns and villages in the activated area. The first main shock was followed in the next day, on 4th of March 2021, by an “equivalent” main shock with Mw6.0 in the adjacent fault segment. These are the largest earthquakes to strike the northeastern part of Thessalia since the M6.3, 1941 Larissa earthquake. The main shocks triggered extensive liquefaction mainly along the banks of the Titarisios tributary where alluvial flood deposits most probably amplified the ground motions. Our seismic monitoring efforts, with the use of recordings of the regional seismological network along with a dense local network that was installed three days after the seismic excitation initiation, led to the improved understanding the geometry and kinematics of the activated faults. The aftershocks form a north–northwest–trending, east–northeast–dipping, ~40 km long distribution, encompassing the two main ruptures along with minor activated structures, consistent with the rupture length estimated from analysis of regional waveform data and InSAR modeling. The first rupture was expanded bilaterally, the second main shock nucleated at its northern tip, where from this second rupture propagated unilaterally to the north–northwest. The focal mechanisms of the two main shocks support an almost pure normal faulting, similar to the aftershocks fault plane solution determined in this study. The strong ground motion of the March 3 main shock was computed with a stochastic simulation of finite fault model. Coseismic displacements that were detected using a dense GPS / GNSS network of five permanent stations located the Thessaly region, have shown an NNE–SSW extension as expected from the nature and location of the causative fault. Coulomb stress changes due to the coseismic slip of the first main shock, revealed that the hypocentral region of the second main shock was brought closer to failure by more than 10 bars.

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.

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

<p>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 ​​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  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.  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  delayed aftershocks. Our study suggests  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.</p>

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.

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. 

Coseismic Slip Distribution of the 24 January 2020 Mw 6.7 Doganyol Earthquake and in Relation to the Foreshock and Aftershock Activities

2020 ◽  
Vol 92 (1) ◽  
pp. 127-139
Author(s):  
Xin Lin ◽  
Jinlai Hao ◽  
Dun Wang ◽  
Risheng Chu ◽  
Xiangfang Zeng ◽  
...  
Keyword(s):  
Seismic Risk ◽  
Body Wave ◽  
Surface Displacement ◽  
Coulomb Stress ◽  
Slip Model ◽  
Coseismic Slip ◽  
Coulomb Stress Changes ◽  
Aftershock Sequences ◽  
Stress Changes ◽  
And Migration

Abstract On 24 January 2020 (UTC), a destructive Mw 6.7 earthquake struck the east Anatolian fault of eastern Turkey after a series of foreshocks, causing many casualties and significant property damage. In this study, the rupture process of this earthquake is investigated with teleseismic broadband body-wave and surface-wave records. Results indicate that this earthquake is a left-lateral strike-slip event, and the rupture extends mainly to south. The main slip patch spreads ∼30  km along strike in the shallow above 14 km with a peak slip of ∼1.2  m, and the total seismic moment is 1.69×1019  N·m. The east–west component of horizontal surface displacement predicted with our slip model ranges from ∼0.4 to −0.3  m. The predicted displacements are consistent with the observed ones obtained from satellite images. We relocate 459 foreshocks and early aftershocks to explore the relationship between foreshock and aftershock sequences and coseismic slip. It is noted that there is an anticorrelation relationship between the distributions of early aftershocks and the coseismic slip. The strain energy in the large slip patch may have been sufficiently released by the mainshock; therefore, fewer early aftershocks occurred in that patch. Although we note a similar pattern between the relocated foreshock and coseismic slip, and a migration of foreshock, our dataset may not well resolve the correlation and migration due to the incomplete relocation foreshock catalog. Based on the slip model, we calculate the coulomb stress changes on the surrounding faults caused by the mainshock. The results reveal that the mainshock promoted stress accumulation on the northern and southern ends of the Elazig–Matalya segment and may reactivate the locked fault segment, leading to a high seismic risk in these regions. Although this earthquake does not significantly increase the coulomb stress change, the seismic risk of the Matalya–Kahraman Maras–Antakya segment should draw attention.

Study on Aftershocks Triggering by Static Stress Changes of the Minxian-Zhangxian 6.6 Earthquake

2014 ◽  
Vol 527 ◽  
pp. 77-80
Author(s):  
Fang Bin Liu ◽  
Ai Guo Wang
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
Elastic Half Space ◽  
Static Stress ◽  
Gansu Province ◽  
Data Sets ◽  
Space Model ◽  
Main Shocks ◽  
Stress Changes ◽  
Better Than

On July 22, 2013, an Ms6.6 earthquake occurred in Minxian-Zhangxian, Gansu Province, China, which caused serious damages. Because of the abundance and clear relationship with the main shocks, aftershocks sequences are typical types of behavior and provide useful data sets. To better understand the aftershocks triggering by static stress changes of the main earthquake, based on Okada’s elastic half-space model, we used accept fault plane consistent with the source and accept fault plane as the optimal models to calculate the stress changes on aftershock focuses by the Minxian-Zhangxian 6.6 Earthquake respectively. The results show that the latter model is better than former, more than 90% of aftershocks located in NWW and SEE, the stress increased areas, which is consistent with strike of Lintan-Tanchang fault (LTF), in other words, the Coulomb static stress changes of the main shock can induce the aftershocks.

scholarly journals Study on Coulomb Stress Triggering of the April 2015 M7.8 Nepal Earthquake Sequence

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Jianchao Wu ◽  
Qing Hu ◽  
Weijie Li ◽  
Dongning Lei
Keyword(s):  
Main Shock ◽  
Earthquake Sequence ◽  
Coulomb Stress ◽  
Coulomb Stress Changes ◽  
Nepal Earthquake ◽  
Rupture Plane ◽  
Stress Changes ◽  
Stress Triggering ◽  
Source Models ◽  
Earthquake Sequences

In April 2015, a M7.8 earthquake occurred less than one month before a M7.3 earthquake near Kodari, Nepal. The Nepal earthquake sequences also include four larger (M > 6) aftershocks. To reveal the interrelation between the main shock and the aftershocks, we check the role of coseismic coulomb stress triggering on aftershocks that follow the M7.8 main shock. Based on the focal mechanisms of the aftershocks and source models of the main shock, the coulomb failure stress changes on both of the focal mechanism nodal planes are calculated. In addition, the coulomb stress changes on the focal sources of each aftershock are also calculated. A large proportion of the M > 6 aftershocks occurred in positive coulomb stress areas triggered by the M7.8 main shock. The secondary triggering effect of the M7.3 aftershock is also found in this paper. More specifically, the M7.3 aftershock promoted failure on the rupture plane of the M6.3 aftershock. Therefore, we may conclude that the majority of larger aftershocks, which accumulated positive coulomb stress changes during the sequence, were promoted or triggered by the main shock failure. It suggests that coulomb stress triggering contributed to the evolution of the Nepal M7.8 earthquake sequence.

scholarly journals Faulting processes during early-stage rifting: seismic and geodetic analysis of the 2009–2010 Northern Malawi earthquake sequence

2019 ◽  
Vol 217 (3) ◽  
pp. 1767-1782 ◽  
Author(s):  
J B Gaherty ◽  
W Zheng ◽  
D J Shillington ◽  
M E Pritchard ◽  
S T Henderson ◽  
...  
Keyword(s):  
Early Stage ◽  
Hanging Wall ◽  
Aftershock Sequence ◽  
Earthquake Sequence ◽  
Local Network ◽  
Rift System ◽  
East African Rift System ◽  
Coseismic Slip ◽  
Fault Interaction ◽  
Main Shocks

SUMMARY In December, 2009, a rare sequence of earthquakes initiated within the weakly extended Western Rift of the East African Rift system in the Karonga province of northern Malawi, providing a unique opportunity to characterize active deformation associated with intrabasinal faults in an early-stage rift. We combine teleseismic and regional seismic recordings of the largest events, InSAR imagery of the primary sequence, and recordings of aftershocks from a temporary (4-month) local network of six seismometers to delineate the extent and geometry of faulting. The locations of ∼1900 aftershocks recorded between January and May 2010 are largely consistent with a west-dipping normal fault directly beneath Karonga as constrained by InSAR and CMT fault solutions. However, a substantial number of epicentres cluster in an east-dipping geometry in the central part of the study area, and additional west-dipping clusters can be discerned near the shore of Lake Malawi, particularly in the southern part of the study area. Given the extensive network of hanging wall faults mapped in the Karonga region on the surface and in seismic reflection images, the distribution of events is strongly suggestive of multiple faults interacting to produce the observed deformation, and the InSAR data permit this but do not require it. We propose that fault interaction contributed to the seismic moment release as a series of Mw 5-to-6 events instead of a normal main shock–aftershock sequence. We find the depth of fault slip during the main shocks constrained by InSAR peaks at less than 6 km, while the majority of recorded aftershocks are deeper than 6 km. This depth discrepancy appears to be robust and may be explained by fault interaction. Structural complexities associated with fault interaction may have limited the extent of coseismic slip during the main shocks, which increased stress deeper than the coseismic slip zone on the primary fault and synthetic faults to the east, causing the energetic aftershock series. There is no evidence of deformation at the Rungwe volcanic province ∼50 km north of the earthquake sequence between 2007 and 2010, consistent with previous interpretations of no significant magmatic contribution during the sequence.

2D finite-element modelling of the interaction between poroelastic effects and viscoelastic relaxation during the seismic cycle

2021 ◽  
Author(s):  
Jill Peikert ◽  
Andrea Hampel ◽  
Meike Bagge
Keyword(s):  
Pore Pressure ◽  
Lower Crust ◽  
Fluid Pressure ◽  
Coulomb Stress ◽  
Viscoelastic Relaxation ◽  
Pore Fluid Pressure ◽  
Coseismic Slip ◽  
Coulomb Stress Changes ◽  
Stress Changes ◽  
Pressure Changes

<p>The analysis of the Coulomb stress changes has become an important tool for seismic hazard evaluation because such stress changes may trigger or delay next earthquakes. Processes that can cause significant Coulomb stress changes include coseismic slip, earthquake-induced poroelastic effects as well as transient postseismic processes such as viscoelastic relaxation. In this study, we investigate the spatial and temporal evolution of pore fluid pressure changes and fluid flow during the seismic cycle, their dependency on the permeability in the crust and the interaction with postseismic viscoelastic relaxation. To achieve this, we use 2D finite-element models for intra-continental normal and thrust faults, which include coseismic slip, poroelastic effects, postseismic viscoelastic relaxation and interseismic stress accumulation. In different experiments, we vary (1) the permeability of the upper and lower crust while keeping the viscosity structure constant and (2) the viscosity of the lower crust and lithospheric mantle, while we keep the permeabilities constant. (1) The modelling results show that the highest changes in pore fluid pressure during and after the earthquake occur within a distance of ~ 1 km around the lower fault tip at the transition between upper and lower crust. The evolution of pore pressure and fluid flow depends primarily on the permeability in the upper crust. With decreasing permeability, the possibility of the pore fluids to flow decreases and thus, in the postseismic phase, the duration of the poroelastic relaxation increases, from a few days to several years, until the pore pressure reaches the initial pressure of the preseismic phase. In contrast, the influence of variations of the permeability in the lower crust on the pore pressure changes is negligible. For high upper-crustal permeabilities, postseismic vertical velocities are high and decreases rapidly with time, from around 120 mm/a after the first year by two orders of magnitude after 10 years, whereas for low permeabilities they remain consistently low over the years after the earthquake. (2) Models with low viscosity of the lower crust show that the timescales of poroelastic effects and viscoelastic relaxation overlap and affect the postseismic velocity already in the early postseismic phase and that both processes decay within a few years after the earthquake. For higher viscosities, the velocity is initially dominated by pore pressure changes during the first few years, whereas viscoelastic relaxation lasts for decades. Both processes also show differences in their spatial scale. Poroelastic effects occur within a few kilometers around the fault, whereas viscoelastic relaxation acts on tens to hundreds of kilometers. As both processes can cause Coulomb stress changes on faults in the vicinity of the earthquake source fault, it is important to understand the spatial and temporal evolution, the effects on the individual faults and the interaction of both processes during the earthquake cycle. Future work will therefore include the calculation and examination of Coulomb stress changes on intra-continental normal and thrust faults using 3D models that include poroelastic effects and viscoelastic relaxation.</p>

scholarly journals Possible triggering of strong earthquakes in a seismic sequence due to Coulomb stress changes generated by the occurrence of previous strong shocks

2001 ◽  
Vol 34 (4) ◽  
pp. 1539
Author(s):  
E. E. PAPADIMITRIOU ◽  
V. G. KARAKOSTAS ◽  
A. B. BABA
Keyword(s):  
Half Space ◽  
Elastic Half Space ◽  
Stress Change ◽  
Coulomb Stress ◽  
Seismic Sequence ◽  
Coseismic Slip ◽  
Strong Earthquakes ◽  
Coulomb Stress Changes ◽  
Stress Changes ◽  
Subsequent Event

Coulomb stress changes (ACFF)were calculated assuming that earthquakes can be modelled as static dislocations in an elastic half-space, and taking into account the coseismic slip in strong earthquakes. The stress change calculations were performed for strike, dip, and rake appropriate to the strong events considered. We evaluate if these chosen earthquakes brought a given strong subsequent event closer to, or farther from, failure. It was found that each of the subsequent strong events occurred in regions of increased calculated Coulomb stress before their occurrence. Moreover, the majority of smaller aftershocks also were located in areas of positive ACFF. This indicates the probable triggering of the latter events, the foci of which are situated at nearby faults or fault segments.

Sign in / Sign up

Export Citation Format

Share Document