scholarly journals Recent seismic activity at Cephalonia island (Greece): a study through candidate electromagnetic precursors in terms of nonlinear dynamics

2015 ◽  
Vol 2 (6) ◽  
pp. 1587-1629 ◽  
Author(s):  
S. M. Potirakis ◽  
Y. Contoyiannis ◽  
N. S. Melis ◽  
J. Kopanas ◽  
G. Antonopoulos ◽  
...  
Keyword(s):  
Seismic Activity ◽  
The West ◽  
Linear Processes ◽  
Hazard Zoning ◽  
Natural Time ◽  
Electromagnetic Emissions ◽  
Critical Characteristics ◽  
Recent Earthquakes ◽  
Electromagnetic Precursors ◽  
Critical Process

Abstract. The preparation process of two recent earthquakes (EQs) occurred in Cephalonia (Kefalonia) island, Greece, (38.22° N, 20.53° E), 26 January 2014, Mw =6.0, depth =21 km, and (38.25° N, 20.39° E), 3 February 2014, Mw =5.9, depth =10 km, respectively, is studied in terms of the critical dynamics revealed in observables of the involved non-linear processes. Specifically, we show, by means of the method of critical fluctuations (MCF), that signatures of critical, as well as tricritical, dynamics were embedded in the fracture-induced electromagnetic emissions (EME) recorded by two stations in locations near the epicenters of these two EQs. It is worth noting that both, the MHz EME recorded by the telemetric stations on the island of Cephalonia and the neighboring island of Zante (Zakynthos), reached simultaneously critical condition a few days before the occurrence of each earthquake. The critical characteristics embedded in the EME signals were further verified using the natural time (NT) method. Moreover, we show, in terms of the NT method, that the foreshock seismic activity also presented critical characteristics before each one of these events. Importantly, the revealed critical process seems to be focused on the area corresponding to the west Cephalonia zone, following the seismotectonic and hazard zoning of the Ionian Islands area near Cephalonia.

scholarly journals Recent seismic activity at Cephalonia (Greece): a study through candidate electromagnetic precursors in terms of non-linear dynamics

2016 ◽  
Vol 23 (4) ◽  
pp. 223-240 ◽  
Author(s):  
Stelios M. Potirakis ◽  
Yiannis Contoyiannis ◽  
Nikolaos S. Melis ◽  
John Kopanas ◽  
George Antonopoulos ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Linear Processes ◽  
Hazard Zoning ◽  
Natural Time ◽  
Non Linear ◽  
Electromagnetic Emissions ◽  
Critical Characteristics ◽  
Recent Earthquakes ◽  
Neighbouring Island ◽  
Electromagnetic Precursors

Abstract. The preparation process of two recent earthquakes (EQs) that occurred in Cephalonia (Kefalonia), Greece, ((38.22° N, 20.53° E), 26 January 2014, Mw = 6.0, depth  ∼  20 km) and ((38.25° N, 20.39° E), 3 February 2014, Mw = 5.9, depth  ∼  10 km), respectively, is studied in terms of the critical dynamics revealed in observables of the involved non-linear processes. Specifically, we show, by means of the method of critical fluctuations (MCF), that signatures of critical, as well as tricritical, dynamics were embedded in the fracture-induced electromagnetic emissions (EMEs) recorded by two stations in locations near the epicentres of these two EQs. It is worth noting that both the MHz EMEs recorded by the telemetric stations on the island of Cephalonia and the neighbouring island of Zante (Zakynthos) reached a simultaneously critical condition a few days before the occurrence of each earthquake. The critical characteristics embedded in the EME signals were further verified using the natural time (NT) method. Moreover, we show, in terms of the NT method, that the foreshock seismic activity also presented critical characteristics before each event. Importantly, the revealed critical process seems to be focused on the area corresponding to the western Cephalonia zone, following the seismotectonic and hazard zoning of the Ionian Islands area near Cephalonia.

scholarly journals Study of electromagnetic emissions associated with seismic activity in Kamchatka region

2001 ◽  
Vol 1 (3) ◽  
pp. 127-136 ◽  
Author(s):  
V. Gladychev ◽  
L. Baransky ◽  
A. Schekotov ◽  
E. Fedorov ◽  
O. Pokhotelov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Data Processing ◽  
Seismic Activity ◽  
Electromagnetic Emission ◽  
Kamchatka Peninsula ◽  
Kamchatka Region ◽  
Radio Transmitters ◽  
Electromagnetic Emissions ◽  
Telluric Currents ◽  
Elf Magnetic Field

Abstract. A review of data processing of electromagnetic emission observation collected at the Complex Geophysical Observatory Karimshino (Kamchatka peninsula) during the first 5 months (July–November, 2000) of its operation is given. The main goal of this study addresses the detection of the phenomena associated with Kamchatka seismic activity. The following observations have been conducted at CGO: variations of ULF/ELF magnetic field, geoelectric potentials (telluric currents), and VLF signals from navigation radio transmitters. The methods of data processing of these observations are discussed. The examples of the first experimental results are presented.

scholarly journals Исмаиллинское землетрясение 5 февраля 2019

2021 ◽  
Author(s):  
G.J. Yetirmishli ◽  
S.S. Ismailova ◽  
S.E. Kazimova
Keyword(s):  
Seismic Activity ◽  
Main Shock ◽  
Source Area ◽  
Strike Slip ◽  
Seismogenic Zone ◽  
Deep Penetration ◽  
The West ◽  
Additional Information ◽  
Basement Faults ◽  
The Right

The Shamakhi-Ismailli seismogenic zone is known as the zone of the most powerful earthquakes in the Caucasus, which has been characterized by high seismic activity for centuries. Analysis of seismicity over the past 15 years has shown an increase in activity in this region. In October 2012, there was a devastating earthquake with a magnitude of 5.3. It is this earthquake that can be considered a trigger of activity in this region in subsequent years. In view of this, the task of studying seismicity, as well as the stress fields of the lithosphere of the region under study, seems to be especially urgent. The study of the seismicity of the Shamakhi-Ismailli zone provides additional information on the deep tectonic processes occurring in this region, which is important for seismic zoning. Aim. The article analyzes the seismic activity of the Shamakhi-Ismailli region, which began with an earthquake on February 5 at 19 h 19 min, with ml = 4.4, which occurred 11 minutes before the main shock with an intensity of 6 points, which occurred on February 5, 2019 at 19 h 31 m. Methods.The epicentral field was studied, as well as the distribution of foci in depth, solutions of the mechanisms of foci of the main shock and the most noticeable aftershock were constructed and analyzed. A diagram of the main elements of the rupture tectonics of the Shamakhi-Ismailli focal zone has been drawn, on which the mechanisms of the focal points of the lakes of the Ismailli field are plotted. Results. It has been established that the source area is located in the zone of intersection of the Vandam longitudinal fault with the West Caspian and transverse Akhsu strike-slip faults, which additionally characterizes the high seismic activity and deep penetration of the West Caspian right-sided orthogonal fault. Thus, it can be seen that, in terms of epicenters, they tend to the basement faults and the nodes of their intersection, i.e. The main shock that occurred on February 5, 2019, shows the agreement of the second nodal plane NP2 with the right-lateral Akhsu and West-Caspian transverse faults characterized by the type of displacement right-lateral strike-slip. An analysis of the orientation of the compression axes showed the NE-SW orientation, and the extension axes of the NW-SE orientation Шамахи-Исмаиллинская сейсмогенная зона известна как зона самых сильных землетрясений на Кавказе, которая на протяжении веков характеризовалась высокой сейсмической активностью. Анализ сейсмичности за последние 15 лет показал рост активности в этом регионе. В октябре 2012 года произошло разрушительное землетрясение магнитудой 5,3. Именно это землетрясение можно считать триггером активности в этом регионе в последующие годы. В связи с этим задача изучения сейсмичности, а также полей напряжений литосферы изучаемого региона представляется особенно актуальной. Изучение сейсмичности Шамахи-Исмаиллинской зоны дает дополнительную информацию о глубинных тектонических процессах, происходящих в этом регионе, что важно для сейсмического районирования. Цель работы.В статье проанализирована сейсмическая активность Шамахы-Исмаиллинского района, начавшаяся землетрясением 5 февраля в 19 ч 19 мин, с ml = 4,4, произошедшим за 11 минут до главного толчка с интенсивностью 6 баллов, произошедшего 5 февраля 2019 в 19 час 31 мин. Методы работы. Изучены эпицентральное поле, распределение очагов по глубине, построены и проанализированы решения механизмов очагов главного толчка и наиболее заметного афтершока. Составлена схема основных элементов разрывной тектоники Шамахы-Исмаиллинской очаговой зоны, на которой нанесены механизмы очагов озер Исмаиллинского месторождения. Результаты работы. Установлено, что очаговая область расположена в зоне пересечения Вандамского продольного разлома с Западно-Каспийским и поперечным Ахсуйским сдвигами, что дополнительно характеризует высокую сейсмическую активность и глубокое проникновение Западно-Каспийского правостороннего ортогонального разлома. Таким образом, видно, что в плане эпицентров они стремятся к разломам фундамента и узлам их пересечения, т.е. главный толчок, произошедший 5 февраля 2019 г., показывает совпадение второй узловой плоскости NP2 с правосторонним Ахсуйским и Западно-Каспийским поперечным разломом, характеризующимися правосторонним сдвиговым типом смещения. Анализ ориентации осей сжатия показал ориентацию СВ-ЮЗ, а оси растяжения – ориентацию СЗ-ЮВ.

Morphotectonic analysis along the northern margin of Samos Island, related to the seismic activity of October 2020, Aegean Sea, Greece

2021 ◽  
Author(s):  
Paraskevi Nomikou ◽  
Dimitris Evangelidis ◽  
Dimitris Papanikolaou ◽  
Danai Lampridou ◽  
Dimitris Litsas ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Normal Fault ◽  
Aegean Sea ◽  
The South ◽  
The West ◽  
Northern Margin ◽  
Hydrographic Survey ◽  
Southern Margin ◽  
Eastern Aegean ◽  
Division Line

<p>On October 30<sup>th</sup> 2020 a strong earthquake of magnitude 7.0 occurred north of Samos Island at the Eastern Aegean Sea. This seismic event was another destructive active deformation in the long seismic history of Samos since the ancient times. Preliminary reports focused the seismic epicenter at about 10 km north of Karlovassi, situated at the western part of the Samos E-W trending coastline. The earthquake mechanism corresponds to an E-W normal fault dipping to the north. The activated fault was assumed to be running along the northern margin of Samos Island, which bounds from the south the Samos basin.</p><p>Immediately after the seismic activity and during the aftershock period in December 2020 an hydrographic survey off the northern coastal margin of Samos Island was conducted with R/V NAUTILOS of the Hellenic Navy Hydrographic Service, using the multibeam SeaBat 7160 RESON. The result of the hydrographic survey was a detailed bathymetric map with 15m grid interval and 50m isobaths.  The main morphological aspects of Samos Basin are a 14 km long, 6 km wide and 690 m deep elongated E-W basin developed north of Samos Island.</p><p>The southern margin of the basin is abrupt with morphological slopes of more than 10<sup>o</sup>, following the major E-W normal fault surface, running along the coastal zone, with an overall throw of more than 500m. In contrast, the northern margin of the basin shows a gradual slope increase towards the south from 1<sup>o</sup> to 5<sup>o</sup>. Numerous small canyons trending N-S transversal to the main direction of the Samos coastline are observed along the southern margin, between 600 and 100 m water depth.  These canyons have a length around 2,7 km and width between 100-300 m. Two large submarine landslides with a canyon width of 1,3 km and 0,8 Km, are located north of Karlovasi. The creation of the canyons is probably due to the uplift of Northern Samos Island and their 500 m vertical height difference corresponds to the average fault throw that has controlled the steep slopes of the margin. The orientation of the fault scarp changes at the western Samos coastline from E-W to ENE-WSW facing the neighboring Ikaria Basin, which is developed to the west of Samos Basin. The division line between the Ikaria and Samos basins runs N-S from the northern slopes and coast of the Kerketeas mountain (1443m). The aftershocks of the 30<sup>th</sup> October main shock are limited east of the N-S division line with only a minor activity 15 km to the west within the eastern margin of the Ikaria Basin.</p>

Transforms are forever

2021 ◽  
Author(s):  
Paola Vannucchi ◽  
David Iacopini ◽  
Jason P. Morgan
Keyword(s):  
Fluid Flow ◽  
Seismic Activity ◽  
Plate Tectonics ◽  
Driving Forces ◽  
Permanent Deformation ◽  
Oceanic Lithosphere ◽  
Ocean Floor ◽  
Spreading Center ◽  
Transform Faults ◽  
Recent Earthquakes

<p>According to Plate Tectonics, fracture zones (FZs) are born at Transform Faults (TFs), which leave behind "inactive" FZs traces as scars on the seafloor that reflect their initial use as one side of a strike-slip transform fault. FZs were originally thought to "heal" as the oceanic lithosphere cooled and strengthened with time. However, the occurrence of recent earthquakes reveals that FZs can be associated with significant seismic activity (for example during the recent Mw 8.6 2012 EQ offshore Sumatra and Mw 7.9 2018 EQ offshore SE Kodiak), and also with permanent deformation that occurs well after passage through the TF.</p><p>The TF at the spreading center is known to be accompanied by the formation of the transform valley which exposes serpentinized peridotite to the ocean floor. Valley relief itself can drive fluid flow that promotes continued serpentinization, and also cooling- and volume-change-linked stress variations. Off-axis seismicity suggests that FZs remain weaker that neighbouring oceanic lithosphere. The transform valley relief in general persists as a fracture zone valley that itself can continue to be a major drive of fluid flow even in the “healed” oceanic lithosphere. After reviewing evidence for FZ activity on (normal) ocean floor we will focus on the long-lived impact of FZs at continental margins. Offshore/onshore evidence of ongoing deformation at FZs is observed through seismic activity at both the western Brazilian and eastern Ghana-Côte d’Ivoire ends of the Romanche FZ. The western Brazil end is also characterized by recent folding and faulting, both offshore across the FZ, and onshore co-linearly with FZ extensions into the continent. Seismic activity in continental Brazil is focused where the FZ intersects the continental margin. This activity suggests that FZs remain as permanent weak lithospheric heterogeneities that are able to store elastic strain.</p><p>The reasons why FZs remain active are still poorly understood. Possible causes include i) effects of serpentinization that occurs both in the TF and in the FZ through hydrothermal fluid/mantle interaction, ii) thermal stress, iii) changing tectonic stresses related to plate driving forces.</p>

scholarly journals Oklahoma’s recent earthquakes and saltwater disposal

2015 ◽  
Vol 1 (5) ◽  
pp. e1500195 ◽  
Author(s):  
F. Rall Walsh ◽  
Mark D. Zoback
Keyword(s):  
Pore Water ◽  
Seismic Activity ◽  
Produced Water ◽  
Active Faults ◽  
Crystalline Basement ◽  
The Public ◽  
The Past ◽  
Basement Faults ◽  
Recent Earthquakes

Over the past 5 years, parts of Oklahoma have experienced marked increases in the number of small- to moderate-sized earthquakes. In three study areas that encompass the vast majority of the recent seismicity, we show that the increases in seismicity follow 5- to 10-fold increases in the rates of saltwater disposal. Adjacent areas where there has been relatively little saltwater disposal have had comparatively few recent earthquakes. In the areas of seismic activity, the saltwater disposal principally comes from “produced” water, saline pore water that is coproduced with oil and then injected into deeper sedimentary formations. These formations appear to be in hydraulic communication with potentially active faults in crystalline basement, where nearly all the earthquakes are occurring. Although most of the recent earthquakes have posed little danger to the public, the possibility of triggering damaging earthquakes on potentially active basement faults cannot be discounted.

The late extension in the inner western Alps: a synthesis along the south-Pelvoux transect

2006 ◽  
Vol 177 (6) ◽  
pp. 299-310 ◽  
Author(s):  
Pierre Tricart ◽  
Jean-Marc Lardeaux ◽  
Stéphane Schwartz ◽  
Christian Sue
Keyword(s):  
Gravitational Collapse ◽  
Seismic Activity ◽  
Western Alps ◽  
Normal Faulting ◽  
The West ◽  
Internal Part ◽  
Orogenic Wedge ◽  
External Domain ◽  
Radial Spreading ◽  
Oriented Parallel

Abstract During the Oligocene, in the central western Alps, tectonic accretion of the external domain to the internal orogenic wedge along the Briançonnais frontal thrust (BFT) was followed by backfolding, resulting in the Alpine fanning structure. The Briançonnais fan axis was rapidly exhumed by erosion. This growing wedge at the scale of the entire Alpine structure was a short-lived situation that ended with the onset of extension in its internal part, before the end Oligocene. To the east, in the Queyras Piedmont Schistes lustrés, extension in ductile then brittle conditions accommodated the tectonic denudation of the Dora-Maira crystalline massif below the Monviso ophiolites, themselves exhumed below the Queyras Schistes lustrés. Consistently, the final cooling of these Schistes lustrés becomes younger eastwards during the Miocene. To the west, inversion of the BFT was directly associated with dense normal faulting in the Briançonnais-Piedmont nappe stack. Local reactivation of thrust surfaces resulted in spectacular trains of tilted blocks oriented parallel and normal to the orogen. When considered at the scale of the entire internal zones, the brittle extension developed during the Neogene globally displays a multitrend character. It is a close to radial spreading that strongly suggests the gravitational collapse of an overthickened crust. Extensional movement along the BFT and multitrend normal faulting in its hangingwall continue at present, resulting in shallow depth seismic activity. From the Neogene onwards, the Alpine structure underwent contrasting tectonic regimes. Extension limited the growth of the internal wedge or accompanied its thinning at least in its upper part. Concurrently the external wedge continued growing through successive folding-thrusting phases.

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