scholarly journals Stochastic analysis of earthquake activity in two seismogenic fault systems in Greece.

2016 ◽  
Vol 47 (3) ◽  
pp. 1099
Author(s):  
Ch. Gkarlaouni ◽  
E. Papadimitriou ◽  
S. Lasocki ◽  
G. Lizurek ◽  
V. Karakostas ◽  
...  
Keyword(s):  
Normal Fault ◽  
Active Regions ◽  
Earthquake Activity ◽  
Earthquake Occurrence ◽  
Seismogenic Fault ◽  
Aegean Area ◽  
Corinth Gulf ◽  
Seismicity Rate ◽  
Event Time ◽  
Smoothed Bootstrap

Possible systematic variations in earthquake occurrence and fluctuations in seismicity behaviourof two seismically active regions in Greece which share common seismotectonic properties, is the aim of this study. Mygdonia graben in northern Greeceis characterized by arather moderate background seismicity, with small earthquakes between 2008-2012 whereas Corinth Gulf in southern Greeceexhibits a constantly high seismicity rate with several seismic activations during the recent instrumental period or before. The statistical approach of seismicity was accomplished, regardingthe magnitude, the inter-event time and distance for recent seismicity as a tool to quantify complex earthquake occurrence ordense spatial andtemporal clustering. For this reason, complete catalogues were compiled for the time period of the study. Probabilistic tests such as the smoothed bootstrap test for modality and bump–hunt were employed in order to unveil the complexity of the probability density function distribution of the above parameters. On the other handspatial earthquake distribution wasalso investigated under the frameof their fractal properties since the fractal coefficientcan largely express the clustering degree of seismicity. The goal of this stochasticanalysisis the quantification of the differentiationin seismicity propertiesinthese two important seismogenic normal fault populations in the back arc Aegean area. 

Seismotectonic analysis of the 2014 seismic swarm at the Western Corinth Gulf (Greece)

2020 ◽  
Author(s):  
Anna Serpetsidaki ◽  
Efthimios Sokos ◽  
Sophie Lambotte ◽  
Pascal Bernard ◽  
Helene Lyon-Caen
Keyword(s):  
Normal Fault ◽  
Active Regions ◽  
Double Difference ◽  
Moment Tensors ◽  
Corinth Gulf ◽  
The North ◽  
Seismicity Distribution ◽  
Triggered Earthquake ◽  
Seismic Swarms ◽  
Pressure Changes

<p>The Corinth Rift (Greece) is one of the most seismically active regions in Europe and has been studied extensively during the past decades. It is characterized by normal faulting and extension rates between 6 and 15 mm yr−1 in an approximately N10E° direction. The seismicity of the area is continuously monitored by the stations of the Corinth Rift Laboratory Network (CRL Net). The availability of a dense permanent seismological network allows the extensive analysis of the seismic swarms which occur frequently. In this study, the September 2014 swarm located at the western part of the Corinth Gulf is analyzed. Initially, more than 4000 automatically located events, of a two month period, were relocated using the HYPODD algorithm, incorporating both catalogue and cross-correlation differential traveltimes. Consequently, the initial seismic cloud was separated into several smaller, densely concentrated clusters. Double difference relocation was also applied to 707 manually located events in order to investigate the Vp/Vs ratio variation, due to its sensitivity in pore fluids. The swarm’s parameters such as seismicity distribution and moment tensors were combined with the seismotectonic data of the area. The results indicate an initial activation of the Psathopyrgos normal fault; afterwards the seismicity extended both towards East and West, while most events occurred at the western part of the study area. The seismicity distribution revealed a main activation of the North – dipping faults. The seismicity migration with respect to pore pressure changes due to fluid movements was investigated through diffusivity calculations. The diffusivity value was found to be 4.5m<sup>2</sup>s<sup>-1</sup>, which is consistent with results of previous studies in the area. The results of the investigation of the fault- zone hydraulic behavior provide evidence for the fluid – triggered earthquake swarms and the related rock physical properties.</p>

Consistency of teleseismic reporting since 1963

1982 ◽  
Vol 72 (1) ◽  
pp. 93-111
Author(s):  
R. E. Habermann
Keyword(s):  
Detection System ◽  
Active Regions ◽  
The United States ◽  
Western Hemisphere ◽  
Cumulative Number ◽  
Data Set ◽  
Seismicity Rate ◽  
Teleseismic Data ◽  
Entire World ◽  
Seismicity Rate Changes

abstract Changes in the rate of occurrence of smaller events have been recognized in the rupture zones of upcoming large earthquakes in several postearthquake and one preearthquake study. A data set in which a constant portion of the events in any magnitude band are consistently reported through time is crucial for the recognition of seismicity rate changes which are real (related to some process change in the earth). Such a data set is termed a homogeneous data set. The consistency of reporting of earthquakes in the NOAA Hypocenter Data File (HDF) since 1963 is evaluated by examining the cumulative number of events reported as a function of time for the entire world in eight magnitude bands. It is assumed that the rate of occurrence of events in the entire world is roughly constant on the time scale examined here because of the great size of the worldwide earthquake production system. The rate of reporting of events with magnitudes above mb = 4.5 has been constant or increasing since 1963. Significant decreases in the number of events reported per month in the magnitude bands below mb = 4.4 occurred during 1968 and 1976. These decreases are interpreted as indications of decreases in detection of events for two reasons. First, they occur at times of constant rates of occurrence and reporting of larger events. Second, the decrease during the late 1960's has also been recognized in the teleseismic data reported by the International Seismological Centre (ISC). This suggests that the decrease in the number of small events reported was related to facets of the earthquake reporting system which the ISC and NOAA share. The most obvious candidate is the detection system. During 1968, detection decreased in the United States, Central and South America, and portions of the South Pacific. This decrease is probably due to the closure of the VELA arrays, BMO, TFO, CPO, UBO, and WMO. During 1976, detection decreased in most of the seismically active regions of the western hemisphere, as well as in the region between Kamchatka and Guam. The cause of this detection decrease is unclear. These detection decreases seriously affect the amount of homogeneous background period available for the study of teleseismic seismicity rate changes. If events below the minimum magnitude of homogeneity are eliminated from the teleseismic data sets the resulting small numbers of events render many regions unsuitable for study. Many authors have reported seismicity rate decreases as possible precursors to great earthquakes. Few of these authors have considered detection decreases as possible explanations for their results. This analysis indicates that such considerations cannot be avoided in studies of teleseismic data.

Sequential modelling of the 2016 Central Italy earthquake cluster using multisource satellite observations and quantitative assessment of Coulomb stress change

2020 ◽  
Vol 221 (1) ◽  
pp. 451-466 ◽  
Author(s):  
Qian Xu ◽  
Qiang Chen ◽  
Jingjing Zhao ◽  
Xianwen Liu ◽  
Yinghui Yang ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Central Italy ◽  
Normal Fault ◽  
Satellite Observations ◽  
Fault System ◽  
Potential Zone ◽  
Seismic Zone ◽  
Seismogenic Fault ◽  
Positive Effects ◽  
Sequence Of Events

SUMMARY A sequence of earthquake events consisting of three large shocks occurred in Central Italy from August to October in 2016 with the duration of almost 2 months. The preliminary study on the seismic mechanism suggests that the sequence of events is the result from the activity of the SW dipping Mt Bove–Mt Vettore–Mt Gorzano normal fault system. For investigation and understanding of the coseismic faulting of the seismogenic fault alignment, we collect a set of comprehensive satellite observations including the Sentinel-1A, ALOS-2/PALSAR-2 and GPS data to map the coseismic surface deformation and estimate the source models in this study. The derived faulting model for the first Amatrice event is characterized by two distinct slip asperities suggesting that it is a predominantly normal dip-slip motion with slight strike-slip component. The second event, Visso earthquake is almost a purely normal rupture. The third Norcia event is dominated by the normal dip-slip rupture of the seismogenic fault, and has propagated up to the ground with significant slip. The three faulting models are then utilized to quantify the Coulomb failure stress (CFS) change over the seismic zone. First, the CFS change on the subsequent two seismogenic faults of the earthquake sequence is estimated, and the derived positive CFS change induced by the preceding earthquakes suggests that the early events have positive effects on triggering the subsequent seismicity. We then explore the response relation of the aftershocks including 961 events with magnitudes larger than M 3.0 to the CFS change over the seismic zone. It suggests that the rupture pattern of the aftershocks is similar to the major shocks with predominantly normal dip-slip. To assess the risk of the future seismic hazard, we analyse quantitatively the spatial distribution of aftershock occurrence and CFS transfer at the seismogenic depth, indicating that the ruptures of the three major shocks do partly release the accumulated strain on the associated fault alignment as well as the dense aftershock, but the CFS increase zone with few aftershocks in the southwest of the eastern Quaternary fault alignment of Central Italy poses the potential of further rupture. In particular, the distribution of aftershock migration also suggests that the north extension of the Mt Bove fault is the potential zone with rupture risk.

scholarly journals Correlation between tectonic CO2 Earth degassing and seismicity is revealed by a 10-year record in the Apennines, Italy

2020 ◽  
Vol 6 (35) ◽  
pp. eabc2938 ◽  
Author(s):  
G. Chiodini ◽  
C. Cardellini ◽  
F. Di Luccio ◽  
J. Selva ◽  
F. Frondini ◽  
...  
Keyword(s):  
Large Scale ◽  
Continuous Process ◽  
Active Regions ◽  
Temporal Relations ◽  
Earthquake Cycle ◽  
Earthquake Occurrence ◽  
Gas Emission ◽  
Seismic Sequences ◽  
Long Time ◽  
High Seismicity

Deep CO2 emissions characterize many nonvolcanic, seismically active regions worldwide, and the involvement of deep CO2 in the earthquake cycle is now generally recognized. However, no long-time records of such emissions have been published, and the temporal relations between earthquake occurrence and tectonic CO2 release remain enigmatic. Here, we report a 10-year record (2009–2018) of tectonic CO2 flux in the Apennines (Italy) during intense seismicity. The gas emission correlates with the evolution of the seismic sequences: Peaks in the deep CO2 flux are observed in periods of high seismicity and decays as the energy and number of earthquakes decrease. We propose that the evolution of seismicity is modulated by the ascent of CO2 accumulated in crustal reservoirs and originating from the melting of subducted carbonates. This large-scale, continuous process of CO2 production favors the formation of overpressurized CO2-rich reservoirs potentially able to trigger earthquakes at crustal depth.

scholarly journals The stones of the Sanctuary of Delphi – Northern shore of the Corinth Gulf – Greece

2020 ◽  
Vol 191 ◽  
pp. 11
Author(s):  
Marilou de Vals ◽  
Renaldo Gastineau ◽  
Amélie Perrier ◽  
Romain Rubi ◽  
Isabelle Moretti
Keyword(s):  
Carbonate Platform ◽  
Hanging Wall ◽  
Normal Fault ◽  
Archaeological Site ◽  
Upper Jurassic ◽  
Coarse Grained ◽  
Corinth Gulf ◽  
Gulf Of Corinth ◽  
Tethys Ocean ◽  
Open Question

The choice of stones by the ancient Greeks to build edifices remains an open question. If the use of local materials seems generalized, allochthonous stones are usually also present but lead to obvious extra costs. The current work aims to have an exhaustive view of the origins of the stones used in the Sanctuary of Delphi. Located on the Parnassus zone, on the hanging wall of a large normal fault related to the Corinth Rift, this Apollo Sanctuary is mainly built of limestones, breccia, marbles, as well as more recent poorly consolidated sediments generally called pôros in the literature. To overpass this global view, the different lithologies employed in the archaeological site have been identified, as well as the local quarries, in order to find their origins. The different limestones are autochthons and come from the Upper Jurassic – Cretaceous carbonate platform of the Tethys Ocean involved in the Hellenides orogen. Those limestones of the Parnassus Massif constitute the majority of the rock volume in the site; a specific facies of Maastrichtian limestone called “Profitis Ilias limestone” has been used for the more prestigious edifices such as the Apollo Temple. The corresponding ancient quarry is located few kilometers west of the sanctuary. Then, slope breccia has been largely used in the sanctuary: it crops out in and around the site and is laying on top of the carbonates. Finally, the pôros appear to be very variable and seven different facies have been documented, including travertine, oolitic grainstone, marine carbonates and coarse-grained sandstones. All these recent facies exist in the south-east shore of the Gulf of Corinth, although – except for the grainstone – the quarries are not yet known.

scholarly journals Seismically active area monitoring by robust TIR satellite techniques: a sensitivity analysis on low magnitude earthquakes in Greece and Turkey

2005 ◽  
Vol 5 (1) ◽  
pp. 101-108 ◽  
Author(s):  
R. Corrado ◽  
R. Caputo ◽  
C. Filizzola ◽  
N. Pergola ◽  
C. Pietrapertosa ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Active Regions ◽  
Space Time ◽  
Data Sets ◽  
Earthquake Occurrence ◽  
Validation Data ◽  
Analysis Technique ◽  
Definition Of ◽  
Area Monitoring ◽  
Low Magnitude

Abstract. Space-time TIR anomalies, observed from months to weeks before earthquake occurrence, have been suggested by several authors as pre-seismic signals. Up to now, such a claimed connection of TIR emission with seismic activity has been considered with some caution by scientific community mainly for the insufficiency of the validation data-sets and the scarce importance attached by those authors to other causes (e.g. meteorological) that, rather than seismic activity, could be responsible for the observed TIR signal fluctuations. A robust satellite data analysis technique (RAT) has been recently proposed which, thanks to a well-founded definition of TIR anomaly, seems to be able to identify anomalous space-time TIR signal transients even in very variable observational (satellite view angle, land topography and coverage, etc.) and natural (e.g. meteorological) conditions. Its possible application to satellite TIR surveys in seismically active regions has been already tested in the case of several earthquakes (Irpinia: 23 November 1980, Athens: 7 September 1999, Izmit: 17 August 1999) of magnitude higher than 5.5 by using a validation/confutation approach, devoted to verify the presence/absence of anomalous space-time TIR transients in the presence/absence of seismic activity. In these cases, a magnitude threshold (generally M<5) was arbitrarily chosen in order to identify seismically unperturbed periods for confutation purposes. In this work, 9 medium-low magnitude (4<Mb<5.5) earthquakes which occurred in Greece and Turkey have been analyzed in order to verify if, even in these cases, anomalous TIR transients can be observed. The analysis, which was performed using 8 years of Meteosat TIR observations, demonstrated that anomalous TIR transients can be observed even in the presence of medium-low magnitude earthquakes (4<Mb<5.5). As far as the research (just started) of possible correlation among TIR anomalies and earthquake occurrence is concerned, such a result suggests that: a) in order to identify seismically unperturbed periods for confutation purposes, a magnitude threshold (at least) lower than 4 should be used; b) the proposed validation/confutation approach should be applied in low-seismicity areas in order to find suitably long seismically quiescent periods.

scholarly journals STRUCTURAL AND EARTHQUAKE EVALUATIONS ALONG JAVA SUBDUCTION ZONE, INDONESIA

2020 ◽  
Vol 30 (1) ◽  
pp. 65
Author(s):  
Adi Patria ◽  
Atin Nur Aulia
Keyword(s):  
Subduction Zone ◽  
Normal Fault ◽  
Thrust Fault ◽  
Earthquake Activity ◽  
Accretionary Wedge ◽  
Forearc Basin ◽  
Plate Interface ◽  
Seafloor Morphology ◽  
Australian Plate ◽  
Seismic Reflection Profiles

Java Subduction is a zone of trench perpendicular convergence of Australian Plate and Southeast Asia in the south of Java. It is characterized by an almost E-W trending trench with an eastward increase of convergence velocity. Three major earthquakes with tsunamis have been caused by deformation along this subduction zone. Although many studies have undertaken to understand the nature of the subduction system, a clear relationship between structures and earthquake activities remains poorly explained. In this study, we used bathymetry, residual bathymetry, and published seismic reflection profiles to evaluate structural and morphological elements, then link the observations to earthquake activity along Java Subduction Zone. Based on seafloor morphology, characteristics of the accretionary wedge and forearc basin varies along the trench in response to the variation of seafloor morphology. Features such as seamounts and ridges which were observed in the oceanic basin may be subducted beneath accretionary wedge and disrupt the morphology of accretionary wedge, forearc basin, and trench. Earthquake activities are generally dominated by normal fault solutions in the trench, which is attributed to plate bending faults while thrust fault solution is observed in the forearc basin area. Thrust fault activities in accretionary wedge are decreased to the east, where there is no thrust fault solution observed in the eastern end of the subduction zone. Few strike-slip focal mechanisms are observed and mainly located within the subducting oceanic plate. Structures and subducting oceanic features may control the earthquake activity where deformation occurred at the edge of these features. The two largest thrust fault earthquakes in 1994 and 2006 are interpreted as a result of deformation along with plate interface on soft or unconsolidated sediment above the incoming plate. The largest normal fault earthquake with a magnitude 8.3 is possibly caused by a crustal scale-fault that breaks the entire oceanic crust.ABSTRAK - Evaluasi struktur dan gempa bumi di sepanjang zona subduksi Jawa, Indonesia. Subduksi Jawa adalah zona konvergensi yang tegak lurus palung antara Lempeng Australia dan Asia Tenggara di selatan Jawa. Hal ini ditandai dengan palung berarah hampir barat–timur dengan peningkatan kecepatan konvergensi ke arah timur. Tiga gempa bumi besar dengan tsunami disebabkan oleh deformasi di sepanjang zona subduksi ini. Meskipun banyak penelitian telah dilakukan untuk memahami sifat sistem subduksi, hubungan antara struktur dan kegiatan gempa bumi masih kurang jelas. Dalam studi ini, kami menggunakan batimetri, batimetri residual, dan profil refleksi seismik untuk mengevaluasi elemen struktur dan morfologi, kemudian menghubungkan pengamatan dengan aktivitas gempa bumi di sepanjang zona subduksi Jawa. Berdasarkan morfologi dasar laut, karakteristik prisma akresi dan cekungan busur muka bervariasi di sepanjang palung sebagai respon terhadap variasi morfologi dasar laut. Fitur seperti seamount dan punggungan yang diamati di cekungan samudera menunjam di bawah prisma akresi dan mengganggu morfologi prisma akresi, cekungan busur muka, dan palung. Aktivitas gempa bumi umumnya didominasi oleh patahan normal di palung, yang dikaitkan dengan patahan tekukan lempeng sedangkan patahan naik diamati di daerah cekungan busur muka. Aktivitas sesar naik di dalam prisma akresi berkurang ke arah timur, di mana tidak ada patahan naik yang teramati di ujung timur zona subduksi. Beberapa mekanisme patahan mendatar diamati dan terutama terletak di dalam lempeng samudera yang menunjam. Struktur dan fitur di kerak samudra yang menunjam dapat mengontrol aktivitas gempa bumi di mana deformasi terjadi di tepian fitur ini. Dua gempa bumi besar dengan sifat patahan naik pada tahun 1994 dan 2006 ditafsirkan sebagai hasil dari deformasi di sepanjang antarmuka lempeng pada sedimen lunak atau tidak terkonsolidasi di atas lempeng yang masuk. Gempa bumi besar dengan sifat sesar normal magnitude 8,3 mungkin disebabkan oleh patahan skala-kerak yang menghancurkan seluruh kerak samudera.

scholarly journals Three-dimensional deformation field analysis of the 2016 Kumamoto Mw 7.1 earthquake

2021 ◽  
Author(s):  
Qingyun Zhang ◽  
Jingfa Zhang ◽  
Yongsheng Li ◽  
Bingqun Li ◽  
Quancai Xie ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Normal Fault ◽  
Deformation Field ◽  
Field Analysis ◽  
Seismogenic Fault ◽  
Kumamoto Earthquake ◽  
The North ◽  
Fault Properties ◽  
Solution Methods ◽  
3D Deformation

Abstract. The Kumamoto earthquake is analyzed mainly with InSAR data combined with strong earthquake and GPS data, using a variety of joint InSAR technology methods and multisource data solution methods and comprehensively considering the normalization and weighting of multisource data. The three-dimensional (3D) deformation field is determined. The results show that the joint solution of multisource data can improve the accuracy of the 3D solution deformation results to a certain extent. From the 3D solution results, the maximum east-west deformation caused by the 2016 Kumamoto earthquake is approximately 2 m; the north-south direction mainly manifests expansion and stretching; the northwestern side subsides vertically, with a maximum subsidence of 2 m; and the southeastern side is uplifted. The horizontal deformation characteristics show that the earthquake is dominated by right-lateral strike-slip; the strike is NE-SW, the dip of the seismogenic fault is nearly vertical, and the Futagawa fault has a few normal fault properties. By analyzing the coseismic 3D deformation field, the seismogenic fault can be better understood, which provides a foundation for studying seismic mechanisms.

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.

Sign in / Sign up

Export Citation Format

Share Document