scholarly journals The November 2019 Seismic Sequence in Albania: Geodetic Constraints and Fault Interaction

2020 ◽  
Vol 12 (5) ◽  
pp. 846 ◽  
Author(s):  
Alessandro Caporali ◽  
Mario Floris ◽  
Xue Chen ◽  
Bilbil Nurce ◽  
Mauro Bertocco ◽  
...  
Keyword(s):  
Moment Tensor ◽  
Stress Transfer ◽  
Elastic Half Space ◽  
Dislocation Model ◽  
Coulomb Stress ◽  
Reverse Fault ◽  
Seismic Sequence ◽  
Fault Interaction ◽  
Before And After ◽  
Dextral Strike Slip Fault

The seismic sequence of November 2019 in Albania culminating with the Mw = 6.4 event of 26 November 2019 was examined from the geodetic (InSAR and GNSS), structural, and historical viewpoints, with some ideas on possible areas of greater hazard. We present accurate estimates of the coseismic displacements using permanent GNSS stations active before and after the sequence, as well as SAR interferograms with Sentinel-1 in ascending and descending mode. When compared with the displacements predicted by a dislocation model on an elastic half space using the moment tensor information of a reverse fault mechanism, the InSAR and GNSS data fit at the mm level provided the hypocentral depth is set to 8 ± 2 km. Next, we examined the elastic stress generated by the Mw = 7.2 Montenegro earthquake of 1979, with the Albania 2019 event as receiver fault, to conclude that the Coulomb stress transfer, at least for the elastic component, was too small to have influenced the 2019 Albania event. A somewhat different picture emerges from the combined elastic deformation resulting after the two (1979 and 2019) events: we investigated the fault geometries where the Coulomb stress is maximized and concluded that the geometry with highest induced Coulomb stress, of the order of ca. 2–3 bar (0.2–0.3 MPa), is that of a vertical, dextral strike slip fault, striking SW to NE. This optimal receiver fault is located between the faults activated in 1979 and 2019, and very closely resembles the Lezhe fault, which marks the transition between the Dinarides and the Albanides.

scholarly journals Coulomb stress transfer and fault interaction over millennia on non-planar active normal faults: the Mw 6.5–5.0 seismic sequence of 2016–2017, central Italy

2017 ◽  
Vol 210 (2) ◽  
pp. 1206-1218 ◽  
Author(s):  
Zoe K. Mildon ◽  
Gerald P. Roberts ◽  
Joanna P. Faure Walker ◽  
Francesco Iezzi
Keyword(s):  
Main Shock ◽  
Central Italy ◽  
Stress Transfer ◽  
Historical Record ◽  
Normal Faults ◽  
Coulomb Stress ◽  
Seismic Sequence ◽  
Fault Interaction ◽  
Slip Rates ◽  
Stress Changes

Abstract In order to investigate the importance of including strike-variable geometry and the knowledge of historical and palaeoseismic earthquakes when modelling static Coulomb stress transfer and rupture propagation, we have examined the August–October 2016 A.D. and January 2017 A.D. central Apennines seismic sequence (Mw 6.0, 5.9, 6.5 in 2016 A.D. (INGV) and Mw 5.1, 5.5, 5.4, 5.0 in 2017 A.D. (INGV)). We model both the coseismic loading (from historical and palaeoseismic earthquakes) and interseismic loading (derived from Holocene fault slip-rates) using strike-variable fault geometries constrained by fieldwork. The inclusion of the elapsed times from available historical and palaeoseismological earthquakes and on faults enables us to calculate the stress on the faults prior to the beginning of the seismic sequence. We take account the 1316–4155 yr elapsed time on the Mt. Vettore fault (that ruptured during the 2016 A.D. seismic sequence) implied by palaeoseismology, and the 377 and 313 yr elapsed times on the neighbouring Laga and Norcia faults respectively, indicated by the historical record. The stress changes through time are summed to show the state of stress on the Mt. Vettore, Laga and surrounding faults prior to and during the 2016–2017 A.D. sequence. We show that the build up of stress prior to 2016 A.D. on strike-variable fault geometries generated stress heterogeneities that correlate with the limits of the main-shock ruptures. Hence, we suggest that stress barriers appear to have control on the propagation and therefore the magnitudes of the main-shock ruptures.

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 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.

A time dependent model of elastic stress in the Central Apennines

2021 ◽  
Author(s):  
Alessandro Caporali ◽  
Joaquin Zurutuza ◽  
Mauro Bertocco
Keyword(s):  
Principal Stress ◽  
Moment Tensor ◽  
Stress Transfer ◽  
Stress Rate ◽  
Coulomb Stress ◽  
Additional Contribution ◽  
Normal Faulting ◽  
Central Apennines ◽  
Regional Stress ◽  
Gnss Network

<p>Seismicity in the Central Apennines is characterized by normal faulting with dip NE-SW near 45°. We show that if the stress at the hypocenter of the 2016 Norcia (Mw=6.5) and 2009 L’Aquila (Mw=6.3 on the Paganica fault) earthquakes originated only from stress transfer from previous historical events occurred in 1315 and 1461 (L’Aquila), 1703 (Montereale plain) and 1703 (Norcia/Valnerina), then the orientation of the principal stress axes would be inconsistent with the observed tensional regime. The additional contribution of a regional stress is thus required to properly align the principal stress axes to those of the moment tensor, but GNSS geodesy provides only stress rates. We empirically estimate a time multiplier for the regional stress rate, computed with a dense GNSS network, such that the principal stress axes resulting from the sum of the stress transferred by previous events and the regional stress rate multiplied by the empirical temporal scale are consistent with normal faulting, both at the L’Aquila and Norcia hypocenters. Based on a Catalogue of 36 events of magnitude larger than 5.6 we estimate the total Coulomb stress at depths and along planes parallel to those of L’Aquila and Norcia. We provide evidence of an asymmetry of the Coulomb stress leading to a stress concentration near the hypocenter of the two events just prior of the 2009 and 2016  earthquakes. This stress anomaly disappeared after the two events. Similar stress patterns are observed for earlier events which took place in 1461 at L’Aquila, 1703 on the Montereale plain and in 1703 at Norcia/Valnerina. The 1997 sequence of Colfiorito exhibits a similar, anisotropic Coulomb stress pattern. Based on the Database of Individual Seismogenic Sources DISS 3.2.1 of INGV we identify as areas of maximum Coulomb stress at present (>2016) the Gran Sasso , the Camerino and Sarnano areas and the area between the San Pio delle Camere, Tocco da Casauria and Sulmona faults.</p>

2-D Analysis of Generalized Thermoelastic Porous Medium under the Effect of Laser Pulse and Microtemperature

2021 ◽  
pp. 2150126
Author(s):  
Amnah M. Alharbi ◽  
Mohamed I. A. Othman ◽  
Elsayed M. Abd-Elaziz
Keyword(s):  
Laser Pulse ◽  
Normal Mode Analysis ◽  
Moment Tensor ◽  
Elastic Half Space ◽  
Mode Analysis ◽  
Gaussian Laser Beam ◽  
Physical Response ◽  
Generalized Thermoelastic ◽  
Non Gaussian ◽  
Graphical Illustration

The paper presents the analytical solutions for a generalized thermoelastic medium consisting of microtemperatures and voids subjected to a laser pulse loading the medium thermally. The 0.02 ps pulse duration of the non-Gaussian laser beam is apt for heating a homogenous isotropic elastic half-space. A method called the normal mode analysis is employed to evaluate numerically the effects of various variables such as the micro-temperature vector, variation in the fraction field of the volume, first heat flux moment tensor, temperature distribution on the stresses and displacement components of the medium. In addition, the graphical illustration of the physical response of the medium has been presented in the presence and absence of void parameters, as well as in the presence of laser pulse with two different acting periods.

scholarly journals Toward Robust and Routine Determination of Mw for Small Earthquakes: Application to the 2020 Mw 5.7 Magna, Utah, Seismic Sequence

2021 ◽  
Author(s):  
James Holt ◽  
Katherine M. Whidden ◽  
Keith D. Koper ◽  
Kristine L. Pankow ◽  
Kevin Mayeda ◽  
...  
Keyword(s):  
Spectral Methods ◽  
Moment Tensor ◽  
Coda Wave ◽  
Strongly Correlated ◽  
Seismic Sequence ◽  
Wave Method ◽  
Direct Wave ◽  
Main Requirement ◽  
Relationship Of

Abstract To better characterize seismic hazard, particularly, for induced seismicity, there is an increasing interest in methods to estimate moment magnitude (Mw) for small earthquakes. Mw is generally preferred over other magnitude types, but, it is difficult to estimate Mw for earthquakes with local magnitude (ML) <3–3.5, using conventional moment tensor (MT) inversion. The 2020 Mww 5.7 Magna, Utah, seismic sequence provides an opportunity to illustrate and evaluate the value of spectral methods for this purpose. Starting with a high-quality seismic catalog of 2103 earthquakes (ML<5.6), we estimate Mw using two independent spectral methods—one based on direct waves, yielding Mw,direct, and the other based on coda waves, yielding Mw,coda. For the direct-wave method, we present a non-parametric (NP) inversion scheme that solves for apparent geometrical spreading, G(R), and site effects (S), similar to other NP procedures that have been used to calibrate regional ML scales. The NP inversion is constrained using Mws derived from MTs for nine events in the Magna sequence. We recover statistically robust and physically reasonable G(R) and S and compute Mw,direct for 635 Magna earthquakes down to ML 0.7. For the coda-wave method, we consider two separate calibration schemes involving previous MT solutions and compute Mw,coda for 311 earthquakes down to ML 1.0. For 280 of the events that were processed with both methods—Mw,direct and Mw,coda—are strongly correlated (r = 0.98), with a mean difference of only 0.05. We compare Mw,direct and Mw,coda with ML and find reasonably good agreement for ML<3.6 with the theoretically predicted relationship of Mw=(2/3)ML+C, in which C is a regional constant. Our results imply that seismic network operators can use spectral-based Mw estimates to replace ML estimates for events with ML≥1.0, and possibly smaller. The main requirement is the existence of a small number of MT solutions for calibration purposes.

scholarly journals The first month of the 2016 central Italy seismic sequence: fast determination of time domain moment tensors and finite fault model analysis of the ML 5.4 aftershock

2016 ◽  
Vol 59 ◽  
Author(s):  
Laura Scognamiglio ◽  
Elisa Tinti ◽  
Matteo Quintiliani
Keyword(s):  
Time Domain ◽  
Moment Tensor ◽  
Central Italy ◽  
Model Analysis ◽  
Fault Model ◽  
Normal Faults ◽  
Seismic Sequence ◽  
Moment Tensors ◽  
Finite Fault ◽  
Finite Fault Model

<p>We present the revised Time Domain Moment Tensor (TDMT) catalogue for earthquakes with M_L larger than 3.6 of the first month of the ongoing Amatrice seismic sequence (August 24th - September 25th). Most of the retrieved focal mechanisms show NNW–SSE striking normal faults in agreement with the main NE-SW extensional deformation of Central Apennines. We also report a preliminary finite fault model analysis performed on the larger aftershock of this period of the sequence (M_w 5.4) and discuss the obtained results in the framework of aftershocks distribution.</p>

scholarly journals Quick regional centroid moment tensor solutions for the Emilia 2012 (northern Italy) seismic sequence

2012 ◽  
Vol 55 (4) ◽  
Author(s):  
Silvia Pondrelli ◽  
Simone Salimbeni ◽  
Paolo Perfetti ◽  
Peter Danecek
Keyword(s):  
Moment Tensor ◽  
Mediterranean Area ◽  
Northern Italy ◽  
Seismic Sequence ◽  
Centroid Moment Tensor ◽  
Strong Earthquakes ◽  
Magnitude Range ◽  
The Mediterranean ◽  
Centroid Moment Tensor Solutions

<p>In May 2012, a seismic sequence struck the Emilia region (northern Italy). The mainshock, of Ml 5.9, occurred on May 20, 2012, at 02:03 UTC. This was preceded by a smaller Ml 4.1 foreshock some hours before (23:13 UTC on May 19, 2012) and followed by more than 2,500 earthquakes in the magnitude range from Ml 0.7 to 5.2. In addition, on May 29, 2012, three further strong earthquakes occurred, all with magnitude Ml ≥5.2: a Ml 5.8 earthquake in the morning (07:00 UTC), followed by two events within just 5 min of each other, one at 10:55 UTC (Ml 5.3) and the second at 11:00 UTC (Ml 5.2). For all of the Ml ≥4.0 earthquakes in Italy and for all of the Ml ≥4.5 in the Mediterranean area, an automatic procedure for the computation of a regional centroid moment tensor (RCMT) is triggered by an email alert. Within 1 h of the event, a manually revised quick RCMT (QRCMT) can be published on the website if the solution is considered stable. In particular, for the Emilia seismic sequence, 13 QRCMTs were determined and for three of them, those with M &gt;5.5, the automatically computed QRCMTs fitted the criteria for publication without manual revision. Using this seismic sequence as a test, we can then identify the magnitude threshold for automatic publication of our QRCMTs.</p>

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