scholarly journals Geodetic Model of the March 2021 Thessaly Seismic Sequence Inferred from Seismological and InSAR Data

2021 ◽  
Vol 13 (17) ◽  
pp. 3410
Author(s):  
Vincenzo De Novellis ◽  
Diego Reale ◽  
Guido Maria Adinolfi ◽  
Eugenio Sansosti ◽  
Vincenzo Convertito
Keyword(s):  
Data Analysis ◽  
Seismic Data ◽  
Surface Deformation ◽  
Stress Transfer ◽  
Normal Fault ◽  
Interferometric Synthetic Aperture Radar ◽  
Seismic Sequence ◽  
Seismic Hazard Estimation ◽  
Large Earthquakes ◽  
Space Time Evolution

In this work, we propose a geodetic model for the March 2021 Thessaly seismic sequence (TSS). We used the interferometric synthetic aperture radar (InSAR) technique and exploited a dataset of Sentinel-1 images to successfully detect the surface deformation caused by three major events of the sequence and constrain their kinematics, further strengthened by seismic data analysis. Our geodetic inversions are consistent with the activation of distinct blind faults previously unknown in this region: three belonging to the NE-dipping normal fault associated with the Mw 6.3 and Mw 6.0 events, and one belonging to the SW-dipping normal fault associated with the Mw 5.6, the last TSS major event. We performed a Coulomb stress transfer analysis and a 1D pore pressure diffusivity modeling to investigate the space–time evolution of the sequence; our results indicate that the seismic sequence developed in a sort of domino effect. The combination of the lack of historical records of large earthquakes in this area and the absence of mapped surface features produced by past faulting make seismic hazard estimation difficult for this area: InSAR data analysis and modeling have proven to be an extremely useful tool in helping to constrain the rupture characteristics.

scholarly journals Multiple Lines of Evidence for a Potentially Seismogenic Fault Along the Central-Apennine (Italy) Active Extensional Belt–An Unexpected Outcome of the MW6.5 Norcia 2016 Earthquake

2021 ◽  
Vol 9 ◽  
Author(s):  
Federica Ferrarini ◽  
Rita de Nardis ◽  
Francesco Brozzetti ◽  
Daniele Cirillo ◽  
J Ramón Arrowsmith ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Tectonic Setting ◽  
Central Italy ◽  
Stress Transfer ◽  
Normal Fault ◽  
Normal Faults ◽  
Coulomb Stress ◽  
Seismic Sequence ◽  
Seismogenic Fault ◽  
Seismogenic Source

The Apenninic chain, in central Italy, has been recently struck by the Norcia 2016 seismic sequence. Three mainshocks, in 2016, occurred on August 24 (MW6.0), October 26 (MW 5.9) and October 30 (MW6.5) along well-known late Quaternary active WSW-dipping normal faults. Coseismic fractures and hypocentral seismicity distribution are mostly associated with failure along the Mt Vettore-Mt Bove (VBF) fault. Nevertheless, following the October 26 shock, the aftershock spatial distribution suggests the activation of a source not previously mapped beyond the northern tip of the VBF system. In this area, a remarkable seismicity rate was observed also during 2017 and 2018, the most energetic event being the April 10, 2018 (MW4.6) normal fault earthquake. In this paper, we advance the hypothesis that the Norcia seismic sequence activated a previously unknown seismogenic source. We constrain its geometry and seismogenic behavior by exploiting: 1) morphometric analysis of high-resolution topographic data; 2) field geologic- and morphotectonic evidence within the context of long-term deformation constraints; 3) 3D seismological validation of fault activity, and 4) Coulomb stress transfer modeling. Our results support the existence of distributed and subtle deformation along normal fault segments related to an immature structure, the Pievebovigliana fault (PBF). The fault strikes in NNW-SSE direction, dips to SW and is in right-lateral en echelon setting with the VBF system. Its activation has been highlighted by most of the seismicity observed in the sector. The geometry and location are compatible with volumes of enhanced stress identified by Coulomb stress-transfer computations. Its reconstructed length (at least 13 km) is compatible with the occurrence of MW≥6.0 earthquakes in a sector heretofore characterized by low seismic activity. The evidence for PBF is a new observation associated with the Norcia 2016 seismic sequence and is consistent with the overall tectonic setting of the area. Its existence implies a northward extent of the intra-Apennine extensional domain and should be considered to address seismic hazard assessments in central Italy.

scholarly journals The Use of Interferometric Synthetic Aperture Radar for Isolating the Contribution of Major Shocks: The Case of the March 2021 Thessaly, Greece, Seismic Sequence

Geosciences ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 191
Author(s):  
Cristiano Tolomei ◽  
Riccardo Caputo ◽  
Marco Polcari ◽  
Nicola Angelo Famiglietti ◽  
Massimiliano Maggini ◽  
...  
Keyword(s):  
Synthetic Aperture Radar ◽  
Surface Deformation ◽  
Ground Movement ◽  
Synthetic Aperture ◽  
Normal Faults ◽  
Interferometric Synthetic Aperture Radar ◽  
Seismic Sequence ◽  
Temporal Separation ◽  
Time Frequency ◽  
Aperture Radar

We study the surface deformation following a moderate size M5+ earthquake sequence that occurred close to Tyrnavos village (Thessaly, Greece) in March 2021. We adopt the interferometric synthetic aperture radar (InSAR) technique to exploit several pairs of Sentinel-1 acquisitions and successfully retrieve the ground movement caused by the three major events (M5+) of the sequence. The mainshocks occurred at depths varying from ~7 to ~10 km, and are related to the activation of at least three normal faults characterizing the area previously unknown. Thanks to the 6-day repeat time of the Sentinel-1 mission, InSAR analysis allowed us to detect both the surface displacement due to the individual analyzed earthquakes and the cumulative displacement caused by the entire seismic sequence. Especially in the case of a seismic sequence that occurs over a very short time span, it is quite uncommon to be able to separate the surface effects ascribable to the mainshock and the major aftershocks because the time frequency of radar satellite acquisitions often hamper the temporal separation of such events. In this work, we present the results obtained through the InSAR data analysis, and are able to isolate single seismic events that were part of the sequence.

Novel geometric classification of 3D seismic and its application to the Habshan clinoforms of Western Oman

2021 ◽  
Vol 40 (3) ◽  
pp. 186-192
Author(s):  
Thomas Krayenbuehl ◽  
Nadeem Balushi ◽  
Stephane Gesbert
Keyword(s):  
Sequence Stratigraphy ◽  
Seismic Data ◽  
Northwestern Part ◽  
Full Potential ◽  
Seismic Sequence ◽  
3D Seismic ◽  
Level Curve ◽  
Seismic Sequence Stratigraphy

The principles and benefits of seismic sequence stratigraphy have withstood the test of time, but the application of seismic sequence stratigraphy is still carried out mostly manually. Several tool kits have been developed to semiautomatically extract dense stacks of horizons from seismic data, but they stop short of exploiting the full potential of seismo-stratigraphic models. We introduce novel geometric seismic attributes that associate relative geologic age models with seismic geomorphological models. We propose that a relative sea level curve can be derived from the models. The approach is demonstrated on a case study from the Lower Cretaceous Kahmah Group in the northwestern part of Oman where it helps in sweet-spotting and derisking elusive stratigraphic traps.

Evidence for contemporary vertical fault displacement from precise leveling data near the New Madrid seismic zone, western Kentucky

1981 ◽  
Vol 71 (6) ◽  
pp. 1933-1942
Author(s):  
F. Steve Schilt ◽  
Robert E. Reilinger
Keyword(s):  
Surface Deformation ◽  
Apparent Movement ◽  
Normal Fault ◽  
Elastic Half Space ◽  
Focal Mechanisms ◽  
New Madrid Seismic Zone ◽  
Seismic Zone ◽  
The Times ◽  
Western Kentucky ◽  
New Madrid

Abstract Relative vertical displacements of bench marks in extreme western Kentucky have been determined by comparison of successive leveling surveys in 1947 and 1968. The resulting pattern of apparent surface deformation shows steep offset which can be closely modeled by a normal fault buried in an elastic half-space. The offset is located near the northern boundary of the Mississippi Embayment and the New Madrid seismic zone, an area where faults have previously been inferred on the basis of both geological and geophysical evidence. If the apparent movement is due to slip along a fault, several lines of evidence (regional structure, earthquake data, and lineations) suggest that the postulated fault trends NNE. Thirteen earthquakes were recorded in this area between the times of leveling; focal mechanisms exist for three of these. The nearest of these three focal mechanisms to the leveling offset implies normal faulting. The magnitude of the earthquake, however, appears to be too small to account for the amount of slip required by the fault model. Thus the apparent deformation may have accumulated with several undetected small earthquakes, or gradually as aseismic creep.

scholarly journals Evolution of surface deformation related to salt extraction-caused sinkholes in Solotvyno (Ukraine) revealed by Sentinel-1 radar interferometry

2020 ◽  
Author(s):  
Eszter Szűcs ◽  
Sándor Gönczy ◽  
István Bozsó ◽  
László Bányai ◽  
Alexandru Szakacs ◽  
...  
Keyword(s):  
Disaster Response ◽  
Surface Deformation ◽  
Characteristic Size ◽  
Interferometric Synthetic Aperture Radar ◽  
Mining Operations ◽  
Data Set ◽  
Linear Feature ◽  
Repetition Time ◽  
Response And Recovery ◽  
Radar Measurements

Abstract. Rocksalt has remarkable mechanical properties and a high economic importance, however, this strength of salt compared to other rocks makes it a rather vulnerable material. Human activities could lead to acceleration of the dissolution of soluble rocksalt and collapse of subsurface caverns. Although sinkhole development can be considered local geological disaster regarding the characteristic size of surface depressions the deformations can result in catastrophic events. In this study we report the spatiotemporal evolution of surface deformation in Solotvyno salt mine area in Ukraine based on Sentinel-1 interferometric synthetic aperture radar measurements. Although the mining operations were finished in 2010 several sinkholes have been opened up since then. Our results show that even though the enormous risk managing efforts the sinkholes continue to expand with a maximum line-of-sight deformation rate of 5 cm/yr. The deformation time series show a rather linear feature and unfortunately no slowdown of the processes can be recognized based on the investigated 4.5 year-long data set. We utilized both ascending and descending satellite passes to discriminate the horizontal and vertical deformations and our results revealed that vertical deformation is much more dominant in the area. With the 6-day repetition time of Sentinel-1 observations the evolution of surface changes can be detected in quasi real-time which can facilitate disaster response and recovery.

Lower Portion Rupture of a Thrust Fault during the 2017 Mw 6.3 Jinghe Earthquake: Implications to Seismic Hazards in the Tian Shan Region

2021 ◽  
Author(s):  
Zongkai Hu ◽  
Tao Li ◽  
Jessica Thompson Jobe ◽  
Xiaoping Yang
Keyword(s):  
Land Surface ◽  
Geometric Model ◽  
Interferometric Synthetic Aperture Radar ◽  
Coseismic Slip ◽  
Surface Mapping ◽  
Strong Earthquakes ◽  
Fault Bend ◽  
Large Earthquakes ◽  
Rupture Pattern ◽  
Tian Shan

Abstract The 2017 Mw 6.3 Jinghe earthquake represents one of the few large earthquakes that are well recorded by seismic instruments and Interferometric Synthetic Aperture Radar (InSAR) observations in the seismically active Tian Shan region. In this study, we use the rupture fault solution (dip, dip direction, and slip sense) from seismologic and InSAR results, along with analysis of our collected surface mapping data, to determine the subsurface fault-plane geometry of the seismogenic Jinghenan fault. This geometric model, integrated with the coseismic slip distribution from seismologic and InSAR data, reveals that: (1) the Jinghenan fault extends downward from the land surface at a dip of ∼46° S (upper ramp), then bends to ∼42° S (lower ramp) at the depth of 9–13 km; (2) the coseismic rupture is confined within the Jinghenan lower ramp, and its upper limitation is approximately coincident with the fault-bend location. This coseismic rupture pattern and seismic behavior can be broadened to other active thrust faults within the Tian Shan, suggesting that, during moderate-strong earthquakes, such faults may only rupture partially in the down-dip extension, and the unruptured fault portion remains to pose high-seismic risk in the future.

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