scholarly journals Short-Term Foreshocks as Key Information for Mainshock Timing and Rupture: The Mw6.8 25 October 2018 Zakynthos Earthquake, Hellenic Subduction Zone

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5681
Author(s):  
Gerassimos A. Papadopoulos ◽  
Apostolos Agalos ◽  
George Minadakis ◽  
Ioanna Triantafyllou ◽  
Pavlos Krassakis
Keyword(s):  
Stress Transfer ◽  
B Value ◽  
Earthquake Catalogue ◽  
Short Term ◽  
Activity Increase ◽  
The North ◽  
Hellenic Arc ◽  
Typical Time ◽  
Real Time Identification ◽  
Transient Intermediate

Significant seismicity anomalies preceded the 25 October 2018 mainshock (Mw = 6.8), NW Hellenic Arc: a transient intermediate-term (~2 yrs) swarm and a short-term (last 6 months) cluster with typical time-size-space foreshock patterns: activity increase, b-value drop, foreshocks move towards mainshock epicenter. The anomalies were identified with both a standard earthquake catalogue and a catalogue relocated with the Non-Linear Location (NLLoc) algorithm. Teleseismic P-waveforms inversion showed oblique-slip rupture with strike 10°, dip 24°, length ~70 km, faulting depth ~24 km, velocity 3.2 km/s, duration 18 s, slip 1.8 m within the asperity, seismic moment 2.0 × 1026 dyne*cm. The two largest imminent foreshocks (Mw = 4.1, Mw = 4.8) occurred very close to the mainshock hypocenter. The asperity bounded up-dip by the foreshocks area and at the north by the foreshocks/swarm area. The accelerated foreshocks very likely promoted slip accumulation contributing to unlocking the asperity and breaking with the mainshock. The rupture initially propagated northwards, but after 6 s stopped at the north bound and turned southwards. Most early aftershocks concentrated in the foreshocks/swarm area. This distribution was controlled not only by stress transfer from the mainshock but also by pre-existing stress. In the frame of a program for regular monitoring and near real-time identification of seismicity anomalies, foreshock patterns would be detectable at least three months prior the mainshock, thus demonstrating the significant predictive value of foreshocks.

Features of degenerative mitral valve prolapse in the North East of China: repair characteristics, and short-term follow-up results

2020 ◽  
Vol 68 (5) ◽  
Author(s):  
Silvia Corona ◽  
Paolo Barbier ◽  
Guangyu Liu ◽  
Osafo A. Annoh ◽  
Marcio Scorsin ◽  
...  
Keyword(s):  
Mitral Valve ◽  
Mitral Valve Prolapse ◽  
Short Term ◽  
North East ◽  
The North

Short-term tilt anomalies preceding local earthquakes near San Jose, California

1980 ◽  
Vol 70 (6) ◽  
pp. 2221-2228
Author(s):  
C. E. Mortensen ◽  
E. Y. Iwatsubo
Keyword(s):  
Partial Recovery ◽  
San Jose ◽  
Short Term ◽  
Origin Time ◽  
Central California ◽  
Local Earthquakes ◽  
The North ◽  
Surface Creep ◽  
The Times ◽  
Black Mountain

abstract A tilt anomaly preceded a pair of earthquakes (ML = 4.2, origin time 0014 UTC, and ML = 3.9, origin time 0018 UTC, both on 29 August 1978) on the Calaveras Fault near San Jose, California. These earthquakes occurred at hypocentral depths of 8.5 and 9.0 km, respectively, and were located 6.7 and 5.2 km northwest of the Mt. Hamilton tiltmeter site. The anomaly is similar in shape and time scale to signals observed on other tiltmeters at the times of recorded surface creep events. The anomaly began approximately 40 hr before the earthquake pair and consisted of gradual down-to-the-east tilting followed by rapid tilting down-to-the-north-northeast at a rate of 12 μrad/hr. This was followed by 1 hr of rapid down-to-the-east tilting amounting to 1.5 μrad. The maximum peak tilt of 10.6 μrad down-to-the-northeast was followed by gradual decelerating tilting down-to-the-southwest constituting partial recovery. An anomaly of nearly identical form, but smaller in amplitude and duration, preceded an ML = 2.2 aftershock on 5 September 1978. Other nearby earthquakes as large as ML = 4.7 have occurred without accompanying creep-like signals. A similar, but a much smaller (0.74 μrad) creep-event-like signal preceded an ML = 3.5 earthquake with epicenter 3 km east of the Black Mountain tiltmeter site. In general, however, short-term tilt anomalies such as these are not observed to precede local earthquakes within the central California tiltmeter network. The tilt signal preceding the 29 August earthquake pair may be interpreted in terms of a model of a propagating creep event, at depth, associated with seismic failure at a “stuck” patch on the fault. However, the data are not adequate to constrain the model sufficiently to constitute a test of the hypothesis.

Influence of Currents and Atmospheric Circulation on the Efficiency of European Anchovy Fishing during its Wintering off the Black Sea Coast of the Krasnodar Territory

2021 ◽  
Author(s):  
B. N. Panov ◽  
E. O. Spiridonova ◽  
◽  
Keyword(s):  
Black Sea ◽  
Atmospheric Transport ◽  
Mesoscale Eddy ◽  
The Black Sea ◽  
Short Term ◽  
European Anchovy ◽  
The North ◽  
Daily Data ◽  
Black Sea Coast ◽  
Sea Coast

Russian fishermen harvest European anchovy primarily off the Black Sea coast of the Krasnodar Territory during its wintering and wintering migrations. At wintering grounds, temperature conditions become a secondary factor in determining the behaviour of commercial concentration of European anchovy, with wind and currents being the primary factors. Therefore, the aim of this work is to determine the potential use of daily data on water circulation and local atmospheric transport in short-term (1–7 days) forecasting of European anchovy fishing in the Black Sea. The research used the European anchovy fishery monitoring materials for January – March 2019, as well as daily maps of the Black and Azov Seas level anomalies (from satellite altimetry data) and surface atmospheric pressure and temperature in Europe (analysis) for the mentioned period. The dynamics of the catch rate and its relation to altimetry and atmospheric transport indicators in the north-eastern part of the Black Sea were investigated using graphical and correlation methods. This analysis showed that the main factor contributing to increased catches is intensification of northwest currents in the coastal 60-km zone. The effect of atmospheric transport on fishing efficiency depends on the mesoscale eddy structure of the nearshore current field. In the presence of an intense northwest current in the fishing area, southwest atmospheric transports have a positive effect on fishing, while in the presence of an anticyclonic meander of currents, northeast atmospheric transports become effective. The presence of maximum significant relationships when the determinants of fishing performance are shifted by 1–7 days allows making short-term predictions of fishing efficiency.

Observations of the Coyote Lake, California earthquake sequence of August 6, 1979

1980 ◽  
Vol 70 (2) ◽  
pp. 559-570 ◽  
Author(s):  
R. A. Uhrhammer
Keyword(s):  
San Francisco ◽  
Fault Zone ◽  
Strong Earthquake ◽  
Main Shock ◽  
B Value ◽  
Aftershock Sequence ◽  
The South ◽  
The North ◽  
Temporal And Spatial Characteristics ◽  
Largest Aftershock

abstract At 1705 UTC on August 6, 1979, a strong earthquake (ML = 5.9) occurred along the Calaveras fault zone south of Coyote Lake about 110 km southeast of San Francisco. This strong earthquake had an aftershock sequence of 31 events (2.4 ≦ ML ≦ 4.4) during August 1979. No foreshocks (ML ≧ 1.5) were observed in the 3 months prior to the main shock. The local magnitude (ML = 5.9) and the seismic moment (Mo = 6 × 1024 dyne-cm from the SH pulse) for the main shock were determined from the 100 × torsion and 3-component ultra-long period seismographs located at Berkeley. Local magnitudes are determined for the aftershocks from the maximum trace amplitudes on the Wood-Anderson torsion seismograms recorded at Berkeley (Δ ≊ 110 km). Temporal and spatial characteristics of the aftershock sequence are presented and discussed. Some key observations are: (1) the first six aftershocks (ML ≧ 2.4) proceed along the fault zone progressively to the south of the main shock; (2) all of the aftershocks (ML ≧ 2.4) to the south of the largest aftershock (ML = 4.4) have a different focal mechanism than the aftershocks to the north; (3) no aftershocks (ML ≧ 2.4) were observed significantly to the north of the main shock for the first 5 days of the sequence; and (4) the b-value (0.70 ± 0.17) for the aftershock sequence is not significantly different from the average b-value (0.88 ± 0.08) calculated for the Calaveras fault zone from 16 yr of data.

scholarly journals Studies of the Movement of Coastal Sea Ice Near Prudhoe Bay, Alaska, U.S.A.

1977 ◽  
Vol 19 (81) ◽  
pp. 533-546 ◽  
Author(s):  
W. F. Weeks ◽  
A. Kovacs ◽  
S. J. Mock ◽  
W. B. Tucker ◽  
W. D. Hibler ◽  
...  
Keyword(s):  
Prediction Models ◽  
Stress Transfer ◽  
Short Term ◽  
Laser Measurements ◽  
A Value ◽  
Pack Ice ◽  
Ice Drift ◽  
Coastal Sea ◽  
Fast Ice ◽  
Prudhoe Bay

Abstract During March-May 1976, a combination of laser and radar ranging systems was used to study the motion of both the fast ice and the pack ice near Narwhal and Cross Islands, two barrier islands located 16 and 21 km offshore in the vicinity of Prudhoe Bay, Alaska. Laser measurements of targets on the fast ice near Narwhal Island indicate small net displacements of approximately 1 m over the period of study (71 d) with short-term displacements of up to 40 cm occurring over 3 d periods. The main motion was outward normal to the coast and was believed to be the result of thermal expansion of the ice. The radar records of fast-ice sites farther offshore show a systematic increase in the standard deviation of the displacements as measured parallel to the coast, reaching a value of ±6.6 m at 31 km. The farthest fast-ice sites show short-term displacements of up to 12 m. There are also trends in the records that are believed to be the result of the general warming of the fast ice with time. Radar targets located on the pack ice showed large short-term displacements (up to 2.7 km) but negligible net ice drift along the coast. There was no significant correlation between the movement of the pack and the local wind, suggesting that coastal ice prediction models can only succeed if handled as part of a regional model which incorporates stress transfer through the pack. The apparent fast-ice-pack-ice boundary in the study area was located in 30-35 m of water.

Memory impairments and its interaction with environmental factors in children aged 6 to 8 years living in gharb plain (N-w of Morocco)

2011 ◽  
Vol 26 (S2) ◽  
pp. 264-264 ◽  
Author(s):  
F.-Z. Azzaoui ◽  
H. Hami ◽  
A.O.T. Ahami
Keyword(s):  
Working Memory ◽  
Environmental Factors ◽  
Building Materials ◽  
Short Term Memory ◽  
Rural Children ◽  
Short Term ◽  
Term Memory ◽  
North West ◽  
Memory Impairments ◽  
The North

IntroductionThe “Gharb” plain (area of our study) localized in the North-West of Morocco is one of the most important agricultural and industrial regions of the Kingdom. Unfortunately, it suffered from the increase of different polluting human activities which expose the population, especially children, to serious neurobehavioral problems.Objective and aimsEvaluation of the short term memory and working memory in urban, periurban and rural schooled children (aged 6 to 8 years) living in Gharb plain and studying the relationship between the performance in this test and the quality of environment.MethodsMemory Sub-test of WISC III (Wechsler Intelligence Scale for Children) and questionnaire about some environmental conditions.ResultsThe obtained results had shown that 3,64% periurban children and 3,03% rural children suffer from short memory impairments and no impairments in urban children were registered. For working memory, 21,05%, 47,06% and 66,67% of impairments were found in urban, periurban and rural children respectively.Moreover, a significant correlations between the performances of short term memory and building materials (p < 0.05), source of pollution near the school (p < 0.05), and consumption of well water (p < 0.001) were registered.ConclusionsThe memory impairments recorded in these children appeared in connection with environmental factors, but a deeper investigation is needed for studying all these factors, in addition to others (psychological, socio-economical, and nutritional) ones.

scholarly journals How Predictable Are the Arctic and North Atlantic Oscillations? Exploring the Variability and Predictability of the Northern Hemisphere

2018 ◽  
Vol 31 (3) ◽  
pp. 997-1014 ◽  
Author(s):  
Daniela I. V. Domeisen ◽  
Gualtiero Badin ◽  
Inga M. Koszalka
Keyword(s):  
Time Scales ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
Prediction Models ◽  
The Arctic ◽  
Ensemble Prediction ◽  
Atmospheric Conditions ◽  
Short Term ◽  
The North ◽  
The North Atlantic Oscillation

ABSTRACT The North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) describe the dominant part of the variability in the Northern Hemisphere extratropical troposphere. Because of the strong connection of these patterns with surface climate, recent years have shown an increased interest and an increasing skill in forecasting them. However, it is unclear what the intrinsic limits of short-term predictability for the NAO and AO patterns are. This study compares the variability and predictability of both patterns, using a range of data and index computation methods for the daily NAO and AO indices. Small deviations from Gaussianity are found along with characteristic decorrelation time scales of around one week. In the analysis of the Lyapunov spectrum it is found that predictability is not significantly different between the AO and NAO or between reanalysis products. Differences exist, however, between the indices based on EOF analysis, which exhibit predictability time scales around 12–16 days, and the station-based indices, exhibiting a longer predictability of 18–20 days. Both of these time scales indicate predictability beyond that currently obtained in ensemble prediction models for short-term predictability. Additional longer-term predictability for these patterns may be gained through local feedbacks and remote forcing mechanisms for particular atmospheric conditions.

Seismicity associated with 2018 and 2020 hydraulic stimulations at EGS in Helsinki, Finland, shows limited earthquake interaction: Implication for seismic hazard assessment

2021 ◽  
Author(s):  
Grzegorz Kwiatek ◽  
Maria Leonhardt ◽  
Patricia Martínez-Garzón ◽  
Matti Pentti ◽  
Marco Bohnhoff ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Hazard Assessment ◽  
Energy Input ◽  
Stress Transfer ◽  
Seismic Hazard Assessment ◽  
B Value ◽  
Temporal Distance ◽  
Probabilistic Seismic Hazard Assessment ◽  
Interevent Time ◽  
Spatio Temporal

&lt;p&gt;In this study we investigate the statistical spatio-temporal characteristics induced seismicity associated with two stimulation campaigns performed in 2018 and 2020 in a 6.1 km deep geothermal well near Helsinki, Finland as part of the St1 Deep Heat project. We aim to find out whether the seismic activity is passively responding to injection operations, or whether we observe signatures of significant stress transfer and strong interactions between events. The former suggests stable relaxation of seismic energy proportional to hydraulic energy input, while the latter includes stress transfer as an additional source of stress perturbation, hence implying larger seismic hazard.&lt;/p&gt;&lt;p&gt;The selected catalogs from 2018 and 2020 stimulation contained in total 60,814 and 4,368 seismic events, respectively, recorded during and after stimulation campaigns and above the local magnitude of M -1.5. The analyzed parameters include magnitude-frequency b-value, correlation integral (c-value), fractal dimension (D-value), interevent time statistics, magnitude correlation, interevent time ratio and generalized spatio-temporal distance between earthquakes. The initial observations suggest significant time-invariance of the magnitude-frequency b-value, and increased D and c-values only at high injection rates, the latter also guiding the rate of seismicity. The seismicity covering the stimulation period neither provide signatures of magnitude correlations, nor temporal clustering or anticlustering. The interevent time statistics are generally characterized with Gamma distribution (close to Poissonian distribution), and the generalized spatio-temporal distance suggest very limited triggering (90% of the catalog was classified as background seismicity). The observable parameters suggest the seismicity passively respond to hydraulic energy input rate with little to no time delay, and the total seismic moment is proportional to total hydraulic energy input. The performed study provides the base for implementation of time-dependent probabilistic seismic hazard assessment for the site.&lt;/p&gt;

A Two-Scale Preparation Phase Preceded an Mw 5.8 Earthquake in the Sea of Marmara Offshore Istanbul, Turkey

2020 ◽  
Vol 91 (6) ◽  
pp. 3139-3147 ◽  
Author(s):  
Virginie Durand ◽  
Stephan Bentz ◽  
Grzegorz Kwiatek ◽  
Georg Dresen ◽  
Christopher Wollin ◽  
...  
Keyword(s):  
Matched Filter ◽  
Aseismic Slip ◽  
Sea Of Marmara ◽  
Spatiotemporal Evolution ◽  
Short Term ◽  
Filter Technique ◽  
The North ◽  
Preparation Phase ◽  
Scale Preparation

Abstract We analyze the spatiotemporal evolution of seismicity during a sequence of moderate (an Mw 4.7 foreshock and Mw 5.8 mainshock) earthquakes occurring in September 2019 at the transition between a creeping and a locked segment of the North Anatolian fault in the central Sea of Marmara, northwest Turkey. To investigate in detail the seismicity evolution, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two largest events are clearly seen, exhibiting two different behaviors: a long-term activation of the seismicity along the entire fault segment and a short-term concentration around the epicenters of the large events. We suggest a two-scale preparation phase, with aseismic slip preparing the mainshock final rupture a few days before, and a cascade mechanism leading to the nucleation of the mainshock. Thus, our study shows a combination of seismic and aseismic slip during the foreshock sequence changing the strength of the fault, bringing it closer to failure.

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