scholarly journals Characteristics of Foreshocks Occurrence of Onshore Earthquakes In Japan For Mj3.0 To 7.2 Mainshocks

2021 ◽  
Author(s):  
Hong Peng ◽  
James Jiro Mori
Keyword(s):  
Earthquake Catalogue ◽  
Spatiotemporal Distribution ◽  
Japan Meteorological Agency ◽  
Earthquake Swarms ◽  
Normal Faulting ◽  
Clear Trend ◽  
Reverse Faulting ◽  
Definition Of

Abstract We use the Japan Meteorological Agency (JMA) earthquake catalogue from 2001 to 2021 to investigate the spatiotemporal distribution of foreshocks for shallow mainshocks (Mj3.0–7.2) that are located onshore of Japan. We find clear peaks for the earlier small earthquakes within 10 days and 3 km prior to the mainshocks, which are considered as our definition of foreshocks. After removing the aftershocks, earthquake swarms and possible earthquakes triggered by the 2011 Mw9.0 Tohoku-oki earthquake, we find that for the 2,066 independent earthquakes, 783 (37.9%) have one or more foreshocks. There is a decreasing trend of foreshock occurrence with mainshock depth. Also, normal faulting earthquakes have higher foreshock occurrence than reverse faulting earthquakes. We calculate the rates of foreshock occurrence as a function of the magnitudes of foreshocks and mainshocks, and we have found no clear trend between the magnitudes of foreshocks and mainshocks.

scholarly journals Global occurrence and impact of small-to-medium magnitude earthquakes: a statistical analysis

2019 ◽  
Vol 18 (1) ◽  
pp. 1-35 ◽  
Author(s):  
Cecilia I. Nievas ◽  
Julian J. Bommer ◽  
Helen Crowley ◽  
Jan van Elk
Keyword(s):  
Statistical Analysis ◽  
Seismic Hazard ◽  
Earthquake Catalogue ◽  
Individual Contribution ◽  
Induced Earthquakes ◽  
A Value ◽  
Magnitude Range ◽  
Hazard And Risk ◽  
Definition Of ◽  
The Impact

Abstract Despite their much smaller individual contribution to the global counts of casualties and damage than their larger counterparts, earthquakes with moment magnitudes Mw in the range 4.0–5.5 may dominate seismic hazard and risk in areas of low overall seismicity, a statement that is particularly true for regions where anthropogenically-induced earthquakes are predominant. With the risk posed by these earthquakes causing increasing alarm in certain areas of the globe, it is of interest to determine what proportion of earthquakes in this magnitude range that occur sufficiently close to population or the built environment do actually result in damage and/or casualties. For this purpose, a global catalogue of potentially damaging events—that is, earthquakes deemed as potentially capable of causing damage or casualties based on a series of pre-defined criteria—has been generated and contrasted against a database of reportedly damaging small-to-medium earthquakes compiled in parallel to this work. This paper discusses the criteria and methodology followed to define such a set of potentially damaging events, from the issues inherent to earthquake catalogue compilation to the definition of criteria to establish how much potential exposure is sufficient to consider each earthquake a threat. The resulting statistics show that, on average, around 2% of all potentially-damaging shocks were actually reported as damaging, though the proportion varies significantly in time as a consequence of the impact of accessibility to data on damage and seismicity in general. Inspection of the years believed to be more complete suggests that a value of around 4–5% might be a more realistic figure.

scholarly journals Distributed earthquake focal mechanisms in the Aegean Sea

2018 ◽  
Vol 40 (3) ◽  
pp. 1125 ◽  
Author(s):  
A. Kiratzi ◽  
C. Benetatos ◽  
Z. Roumelioti
Keyword(s):  
Aegean Sea ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Normal Faulting ◽  
Small Magnitude ◽  
The North ◽  
Earthquake Focal Mechanisms ◽  
Reverse Faulting ◽  
Different Types ◽  
Transform Fault Zone

Nearly 2,000 earthquake focal mechanisms in the Aegean Sea and the surroundings for the period 1912- 2006, for 1.5 <M<7.5, and depths from 0 to 170 km, indicate a uniform distribution and smooth variation in orientation over wide regions, even for the very small magnitude earthquakes. ~ 60% of the focal mechanisms show normal faulting, that mainly strikes ~E-W. However, a zone ofN-S normal faulting runs the backbone of Albanides-Hellenides. Low-angle thrust and reverse faulting is confined in western Greece (Adria-Eurasia convergence) and along the Hellenic trench (Africa-Eurasia). In the central Aegean Sea the effect of the propagating tip of the North Anatolian Fault into the Aegean Sea is pronounced and strike-slip motions are widely distributed. Shearing does not cross central Greece. Strike-slip motions reappear in the Cephalonia-Lefkada Transform Fault zone and in western Péloponnèse, which shows very complex tectonics, with different types of faulting being oriented favourably and operating under the present stress-field. Moreover, in western Péloponnèse the sense of the observed shearing is not yet clear, whether it is dextral or sinistral, and this lack of data has significant implications for the orientation of the earthquake slip vectors compared to the GPS obtained velocity vectors.

Fault failure modes, deformation mechanisms, dilation tendency, slip tendency, and conduits v. seals

2019 ◽  
Vol 496 (1) ◽  
pp. 75-98 ◽  
Author(s):  
David A. Ferrill ◽  
Kevin J. Smart ◽  
Alan P. Morris
Keyword(s):  
Stress Field ◽  
Failure Modes ◽  
Deformation Behaviour ◽  
Deformation Mechanisms ◽  
Volume Loss ◽  
Fault Geometry ◽  
Normal Faulting ◽  
Mechanical Stratigraphy ◽  
Slip Tendency ◽  
Reverse Faulting

AbstractFaults have complicated shapes. Non-planarity of faults can be caused by variations in failure modes, which in turn are dictated by mechanical stratigraphy interacting with the ambient stress field, as well as by linkage of fault segments. Different portions of a fault or fault zone may experience volume gain, volume conservation and volume loss simultaneously depending on the position along a fault's surface, the stresses resolved on the fault and the associated deformation mechanisms. This variation in deformation style and associated volume change has a profound effect on the ability of a fault to transmit (or impede) fluid both along and across the fault. In this paper we explore interrelated concepts of failure mode and resolved stress analysis, and provide examples of fault geometry in normal faulting and reverse faulting stress regimes that illustrate the effects of fault geometry on failure behaviour and related importance to fluid transmission. In particular, we emphasize the utility of using relative dilation tendency v. slip tendency on fault patches as a predictor of deformation behaviour, and suggest this parameter space as a new tool for evaluating conduit v. seal behaviour of faults.

scholarly journals Migration diffusivity as a controlling factor in the duration of earthquake swarms

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Yuta Amezawa ◽  
Takuto Maeda ◽  
Masahiro Kosuga
Keyword(s):  
Time Windows ◽  
Published Data ◽  
Earthquake Swarms ◽  
Fluid Viscosity ◽  
Temporal Behavior ◽  
Northeastern Japan ◽  
Triggered Earthquake ◽  
Definition Of ◽  
The Relationship ◽  
Swarm Activity

AbstractEarthquake swarms exhibit highly uncertain temporal behavior. We investigated the relationship between the swarm duration and the diffusivity of hypocenter migration for triggered earthquake swarms in northeastern Japan. These parameters were systematically estimated by applying a diffusion model and using a unified definition of time windows for the initial and final stages of swarm activity. This approach detected a clear negative correlation between the diffusivity and swarm durations. The relation follows a power-law with an exponent of $$-\,0.5$$ - 0.5 to $$-\,1.0$$ - 1.0 . Examination of published data confirmed that this relationship globally holds under various localities and tectonic environments. These results suggest that diffusivity, and by extension, crustal permeability and fluid viscosity play a key role in controlling the duration of the fluid-driven swarms.

Fault tectonic analysis of aftershocks of the 2011 Tohoku, Japan, earthquake: interaction between three different tectonic domains and approximation of stress magnitude

2020 ◽  
Author(s):  
Pom-yong Choi
Keyword(s):  
Subduction Zone ◽  
Continental Crust ◽  
Focal Mechanism ◽  
Coastal Area ◽  
Pacific Plate ◽  
Japan Meteorological Agency ◽  
Vertical Load ◽  
Normal Faulting ◽  
Stress Tensors ◽  
The Pacific

&lt;p&gt;In order to elucidate the regional variation of stress field in the eastern part of Japan after the 2011 Tohoku earthquake of M=9.3, we tried to analyze focal mechanism data of earthquakes that occurred in 2011, presented by the Japan Meteorological Agency (JMA). Although earthquakes (aftershocks) occurred largely in the offshore area along the subduction zone of the Pacific plate under the North American and Eurasian plates, focal mechanism data presented by JMA are mainly those on land. For fault tectonic analysis, the suggested focal mechanism data are classified into appropriate populations on the basis of clusters and focal depths to reduce the bias and errors of stress tensors resulting from areal stress variation and varying vertical load. According to the results, the stress types of determined stress tensors consist of reverse, wrench and normal faulting ones. As for reverse faulting stresses in which the vertical load is the minimum principal stress axis, those of NW-SE compression prevail, which may be tightly related to northwestward movement of the Pacific plate. Those of E-W compression are determined in the continental crust deeper than about 9 km around Yamagata and in the lower part of subducting oceanic crust. In the Kanagawa and Chiba areas, determined stress tensors display NNW-SSE compression as well as NW-SE and E-W compressions. The NNW-SSE compression seems to be related to the movement of the Philippine Sea plate. Stress tensors of wrench faulting type are found in the continental crust far from the subduction zone of the Pacific plate, displaying NW-SE and E-W compressions in the shallower and deeper parts of crust, respectively. The E-W compression is presumably associated with the Himalayan tectonic domain. Determined stress tensors of normal faulting type show diverse extension directions: NW-SE extension in the coastal area, parallel to the Pacific compression, and E-W or NE-SW extension elsewhere. Especially, numerous focal mechanism data showing normal faulting stresses are present in the coastal area of Fukushima and Ibaraki, from which Poisson&amp;#8217;s ratio of shallow crust was determined to be 0.25 to 0.27 using friction lines on Mohr&amp;#8217;s circles and focal depths (or corresponding vertical loads). Additional horizontal stress related to the northwestward motion of the Pacific plate was estimated to be 46, 122 and 286 MPa in three groups of 0 to1.5, 1.5 to 4.5 and 3.5 to 11.5 kilometers in depth, respectively.&lt;/p&gt;

Estimating earthquake magnitude

1967 ◽  
Vol 57 (4) ◽  
pp. 747-758
Author(s):  
Helen W. Freedman
Keyword(s):  
United States ◽  
Probability Distribution ◽  
The United States ◽  
Geodetic Survey ◽  
Earthquake Magnitude ◽  
Earthquake Catalogue ◽  
Definition Of ◽  
Theoretical Considerations ◽  
Large Earthquakes ◽  
Good Agreement

abstract The disturbingly large variation in magnitude estimates observable in any earthquake catalogue has led to this analysis of one particular catalogue and definition of magnitude. The method employed by the United States Coast and Geodetic Survey is analyzed in the light of theoretical considerations concerning the probability distribution of the variables involved. In particular, the truncation procedure seems to lead to estimates which consistently underestimate the magnitude for large earthquakes, and perhaps overestimate the magnitude for small ones. An alternative method is suggested which leads to estimates which are in good agreement with those provided by Berkeley, Pasadena and Lamont.

scholarly journals Blurring the Definition of Employment Relations in Russia: Case Law on the General Notion and Some Atypical Forms of Labor

Teisė ◽  
2019 ◽  
Vol 113 ◽  
pp. 190-204
Author(s):  
Nikita Lyutov
Keyword(s):  
Labor Relations ◽  
Case Law ◽  
General Notion ◽  
Employment Relations ◽  
Labour Law ◽  
Clear Trend ◽  
Employment Relationships ◽  
Temporary Agency Work ◽  
Definition Of

Transformation of Russian labour law in the last decades shows the clear trend to differentiation and fragmentation with constantly growing number of special norms covering specific (atypical) types of employment relationships. At the same time modern labour law reflects only some of recently appearing forms of employment, such as temporary agency work or telework. The paper deals with the definition of labor relations and some atypical forms of employment.

Introductory paper

1966 ◽  
Vol 24 ◽  
pp. 3-5
Author(s):  
W. W. Morgan
Keyword(s):  
Line Intensity ◽  
Classification Scheme ◽  
Two Dimensional ◽  
Spectral Classification ◽  
Dimensional Array ◽  
Rr Lyrae ◽  
Metallic Line ◽  
Introductory Paper ◽  
Parameter Varying ◽  
Definition Of

1. The definition of “normal” stars in spectral classification changes with time; at the time of the publication of theYerkes Spectral Atlasthe term “normal” was applied to stars whose spectra could be fitted smoothly into a two-dimensional array. Thus, at that time, weak-lined spectra (RR Lyrae and HD 140283) would have been considered peculiar. At the present time we would tend to classify such spectra as “normal”—in a more complicated classification scheme which would have a parameter varying with metallic-line intensity within a specific spectral subdivision.

Random isn't real: How the patchy distribution of ecological rewards may generate “incentive hope”

2019 ◽  
Vol 42 ◽  
Author(s):  
Laurel Symes ◽  
Thalia Wheatley
Keyword(s):  
Natural Environment ◽  
Random Distribution ◽  
Spatiotemporal Distribution ◽  
Patchy Distribution ◽  
Distribution Of Resources

AbstractAnselme & Güntürkün generate exciting new insights by integrating two disparate fields to explain why uncertain rewards produce strong motivational effects. Their conclusions are developed in a framework that assumes a random distribution of resources, uncommon in the natural environment. We argue that, by considering a realistically clumped spatiotemporal distribution of resources, their conclusions will be stronger and more complete.

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