earthquakes and faulting

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A tectonic interpretation of NW SE strike slip faulting during the 2004 off the Kii peninsula earthquakes, Japan: Probable tear of the Philippine Sea plate

A tectonic interpretation of NW SE strike slip faulting during the 2004 off the Kii peninsula earthquakes, Japan: Probable tear of the Philippine Sea plate

We present a tectonic interpretation of NW-SE trend- ing strike-slip faulting during the 2004 off the Kii penin- sula earthquakes, which has not yet been discussed. By reviewing the rupture mode of the 2004 earthquakes and re-examining Miyoshi and Ishibashi’s (2004) inference of a PHS slab tear beneath the Kii Peninsula, we propose a hy- pothesis that there exists a NW-SE striking tear or a strongly distorted narrow belt of the PHS plate continuously from the ocean side of the Nankai trough to the deeper part beneath the Kii Peninsula. We interpret that NW-SE trending strike- slip faulting in the 2004 earthquakes was a partial rupture of this tear and played an important role during the earth- quake sequence. Along the slab tear beneath the Kii Penin- sula, two M 7-class disastrous earthquakes seem to have occurred in 1899 and 1952. Further investigation is neces- sary to clarify the true nature and the tectonic significance of this tear of the PHS plate.

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On the complexity of surface ruptures during normal faulting earthquakes: excerpts from the 6 April 2009 L’Aquila (central Italy) earthquake ( w6.3)

On the complexity of surface ruptures during normal faulting earthquakes: excerpts from the 6 April 2009 L’Aquila (central Italy) earthquake ( w6.3)

From this perspective, the work and the ideas we presented have obvious and important implications in the context of seismic hazard assessment. The “. . . ability to distinguish be- tween tectonically induced primary and secondary faulting, faulting induced by strong ground motions, and faulting in- duced by nontectonic phenomena . . . ” has been seen by Han- son et al. (1999) as a fundamental pre-requisite for devising appropriate regulatory criteria in the siting of nuclear power plants and other critical facilties. McCalpin (2000), among several others, discussed strategies for the analysis of sec- ondary features associated with the distributed expression of reverse faulting, including bending-moment faults, flexural- slip faults and folds, and placed them in a hierarchical classi- fication. Much of their work, however, deals with secondary faulting induced by blind faults in compressional environ- ments, because this is the dominating tectonic style in the countries where these studies were initiated. So far there has been little appreciation for the fact that the same features and interpretative problems may also be seen in extensional en- vironments: our study aims to fill this gap using the unique evidence from the 2009 earthquake.

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A 2006 Colima Rift Earthquakes Series and Its Relationship to the Rivera-Cocos Plate Boundary

A 2006 Colima Rift Earthquakes Series and Its Relationship to the Rivera-Cocos Plate Boundary

Abstract: From 31 July through 13 August 2006 a series of fourteen earthquakes (M 3.9 to 6.1) occurred in the western end of the Central Mexican Volcanic Belt (CMVB) in a twenty-five days period. The most prominent earthquake (Mw 6.1) occurred on 11 August 2006 at 14:30 UTC (9:30 local time) approximately at 18.37° N, 101.25° W and 81 km depth. The epicenter was less than 40 km from Huetamo, Michoacan a 41,250-inhabitant city and 60 km from the El Infiernillo dam embayment the third largest hydroelectric plant in Mexico. This earthquake was widely felt with minor to moderate reported damage. In Mexico City 250 km away from the epicenter the earthquake produced alarm among the population and several buildings were evacuated. The earthquakes series developed into two activity clusters one centered in the coast and separated about 300 km from a second inland cluster. The initial coastal cluster consisted of a nearly linear activity distribution, which includes shallow-depth earthquakes of reverse and normal faulting mechanisms. The inland cluster shows more compact and deeper hypocenters distribution. Earthquakes first-motion polarities indicate that ruptures occurred as a normal faulting, which is a characteristic of the CMVB earthquakes. The overall trend of earthquakes distribution shows two branches, one, along the El Gordo-Colima graben system direction (~N45°E) nearly perpendicular to the coast and another along an east-west direction parallel to the southern border of the CMVB. Our results indicate that these two branches might constitute part of the continental extension of the Rivera-Cocos plate boundary.

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Localized extensional tectonics in an overall reverse-faulting regime, Northeast Japan

Localized extensional tectonics in an overall reverse-faulting regime, Northeast Japan

The 2011 Tohoku-Oki earthquake was an unprece- dented megathrust earthquake, monitored by the dense nationwide, high-sensitivity seismograph network (Hi- net) and global navigation satellite system (GNSS). A large number of studies have been reported since the earthquake, based on multiple lines of evidence identi- fied in geological, geophysical and geochemical data (e.g., Somerville 2015; Hasegawa and Yoshida 2015). The amount and quality of various data can advance our understanding of earth and planetary sciences, including megathrust earthquakes in the subduction zone. Espe- cially, geophysical findings of crustal heterogeneities and geological records of crustal deformation provide a clue to the mechanism for the generation of localized exten- sional tectonics in an overriding compressional island- arc crust. In this review, I focus on seismotectonics before and after the Tohoku-Oki earthquake, the details of seismic velocity structure and electrical resistivity structure in the seismogenic zone, and vertical crus- tal deformation for the late Pleistocene and the present time.

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Seismogeodetic Imaging of Active Crustal Faulting

Seismogeodetic Imaging of Active Crustal Faulting

The inter-seismic strain accumulation along the central SJF is characterized by strong fault-normal gradients. To fit such high strain rates, geodetic inversions assuming a dislocation model require the Anza segment to be locked from the surface to a relatively shallow depth of 10.4 ± 1.3 km (Lindsey, Sahakian, et al., 2014). In con- trast, the maximum depth of seismicity, which we define as the depth above which 95% of the earthquakes occur, is 16.5 km (Smith-Konter, Sandwell, and P. Shearer, 2011). A possible mechanism that may contribute to the high strain rates observed at the surface, and thus to reconcile the seismic and geodetic observations in Anza, is transient deep fault creep (Wdowinski, 2009). According to this view, the deep transition between fully locked and steady slipping portions of the fault consists of aseismically creeping patches, capable of sustaining transients, interspersed by seis- mogenic asperities whose dynamic failure results in microseismicity. The topology of the asperities and the heterogeneity of frictional properties within the transition zone account for the statistics of the earthquake catalog. As has been observed in a number of subduction zones (Schwartz and Rokosky, 2007), aseismic release of strain accumulated in the transition zone beneath the SJF could manifest itself by deep intermittent creep events as well as by the occurrence of tectonic tremors. Since the sensitivity of surface deformation to deep slip is small, it is expected that tectonic tremors, if they occur, will provide useful constraints on transient defor- mation in the transition zone. To date, compelling evidence for the occurrence of tectonic tremors near Anza has not been presented.

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Photographic evidence of luminescence during faulting in granite

Photographic evidence of luminescence during faulting in granite

Some earthquakes produce lights and illumination of the sky before and during seismic rupture. This phe- nomenon, earthquake light, is a typical example of a macroscopic anomaly associated with earthquakes. Anec- dotes of such luminous phenomenon are reported in an- cient Egyptian, Chinese, and Japanese documents (Musha, 1931; Terada, 1931; Derr, 1973; Ikeya and Takaki, 1996). Photographic evidence of the earthquake light obtained during earthquake swarm activities in Matsushiro, Japan, in 1960s, caught the attention of geophysicists (Yasui, 1968, 1971; Derr, 1986). Similar sightings were reported in the M 7.2 1995 Hyogoken-nambu (Kobe) Earthquake (Tsukuda, 1997; Kamogawa et al., 2005), which height- ened public interest in this phenomenon. Despite popular interest on this phenomenon, which could be an immedi- ate earthquake precursor, scientific research on earthquake light has been limited. How such a luminous phenomenon occurs, and whether and how it relates to faulting processes is not well understood, but given that luminescence com- monly appears during the fracture of brittle material, several promising hypotheses have been proposed in which earth- quake light is linked either to pre-seismic stress accumula- tion or co-seismic faulting (Scholz, 1972; Lockner et al., 1983; Schloessin, 1985; Brady and Rowell, 1986; Derr, 1986; Freund, 2003).

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Estimation of Far-field Coseismic Deformation Caused by the Recent Giant Earthquakes

Estimation of Far-field Coseismic Deformation Caused by the Recent Giant Earthquakes

In the early 21th century, two giant earthquakes occurred: the 26 December 2004 M9.1 Sumatra earthquake [1] and the 11 March 2011 M9.0 Tohoku earthquake [2]. These earthquakes occurred at about 1000 km and 4000 km distance from Vietnam, respectively, if we refer to epicenters. The 2004 Sumatra earthquake ruptured at least 1200 km of the megathrust along the plate boundary between the Indian - Australian plate and the Eurasian plate. Its epicenter located the southernmost end of the source region. Thus, the distance from the study area to the earthquake epicenter is shorter (about 800 km). While, the 2011 Tohoku earthquake is the largest seismic event occurred after the 2004 Sumatra earthquake. This event occurred near the northeastern coast of Honshu Island, Japan, as a result of thrust faulting caused by the Pacific plate subduction beneath the Japan Island Arc. The fault rupture is characterized by a compact region of high-slip of about 450 km long and about 200 km wide localized near the trench with a large maximum slip up to 60 m [3].

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Investigating the mechanics of earthquakes using macroscopic seismic parameters

Investigating the mechanics of earthquakes using macroscopic seismic parameters

We next try to address the issue of the mechanisms of deep earthquake faulting, a problem that has invoked significant interest through the years, and whether our results help us understand this problem better. Since we cannot envisage ordinary brittle failure at the pressures and temperatures at which deep earthquakes occur, several mechanisms have been proposed to explain deep earthquakes. Some of the suggested mechanisms include 1) dehydration embrittlement, where brittle fracture is induced by the release of volatiles which serve to increase the pore pressure and thus reduce the effective stress on the fault [Meade and Jeanloz, 1991]; 2) transformational faulting where phase changes cause faulting due to the rapid growth of an anticrack and the resulting thermal runaway processes cause the fault to grow catastrophically [Green II and P.C., 1989]; and 3) creep induced shear instabilities and melting where deformation of a material occurs rapidly enough compared to the timescale of thermal diffusion so that heat is accumulated in regions of high-strain and a positive feedback between deformation-induced heating and deformation leads to thermal runaway [Karato et al., 2001]. There have been several attempts to use seismological parameters to constrain the faulting mechanism [Frolich, 1989; Green II and Houston, 1995] and the more recent studies [Wiens, 2001; Karato et al., 2001] favor creep induced shear instabilities as the more probable mechanism for deep earthquake faulting.

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A model for aperiodicity in earthquakes

A model for aperiodicity in earthquakes

In the early 80s, rate and state dependent frictions laws have shown to be qualified in reproducing some behavior similar to that of earthquake faulting. Burridge and Knopoff incorporated a friction term in their model that was depen- dent on the block’s velocity, but studies were later made that indicated that the friction term could not be a single valued function of velocity (Marone, 1998). Improvements to the BK friction law were made by Dieterich, Ruina, Rice and others based on empirical studies of rock friction in the lab- oratory. They discovered that the incorporation of a state variable enabled the model to exhibit almost entirely the ob- served seismic behaviors such as stick-slip phenomena, fault healing and memory effects (Ruina, 1983), (Marone, 1998). Carlson and Batista (1996) developed further constitutive re- lations to describe the friction in a lubricated interface, with the state variable representing the degree of melting in the lubricant layer. Daub and Cralon (2007) 1 have studied fault- scale behavior of various friction laws (including Dieterich- Ruina style friction) and their implications for dynamic rup- ture.

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Width of surface rupture zone for thrust earthquakes: implications for earthquake fault zoning

Width of surface rupture zone for thrust earthquakes: implications for earthquake fault zoning

DRs were measured every 200 m along-strike the PF. In or- der to prevent short ruptures being missed or under-sampled during measurement, ruptures shorter than 200 m were mea- sured at the midpoint, and ruptures between 200 and 400 m long were measured at the midpoint and endpoints (Fig. 1). Moreover, all the points having displacement information on DRs were measured. All the points with displacement values on the PF rupture were also measured if DRs were associated with that strand of the PF. A particular metrics was used for the Sylmar segment of the San Fernando 1971 rupture zone (Fig. S1), where most of the distributed faulting was mapped along roads, resulting in a very discontinuous pattern of sur- face ruptures. In order to have a database of measurements statistically equivalent with respect to the other studied earth- quakes, various measurement logics were used in order to sample ruptures at distances that equal more or less 200 m (see Fig. S1 for details).

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Earthquake forecasting and its verification

Earthquake forecasting and its verification

A variety of studies have utilized variations in seismicity over relatively large distances to forecast future earthquakes. The distances are large relative to the rupture dimension of the subsequent earthquake. These approaches are based on the concept that the earth’s crust is an activated thermodynamic system (Rundle et al., 2003). Among the evidence for this be- havior is the continuous level of background seismicity in all seismographic areas. About a million magnitude two earth- quakes occur each year on our planet. In southern Califor- nia about a thousand magnitude two earthquakes occur each year. Except for the aftershocks of large earthquakes, such as the 1992 M = 7.3 Landers earthquake, this seismic activity is essentially constant over time. If the level of background seismicity varied systematically with the occurrence of large earthquakes, earthquake forecasting would be relatively easy. This, however, is not the case.

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Surface latent heat flux as an earthquake precursor

Surface latent heat flux as an earthquake precursor

pixel covering epicenter of the earthquakes at the center. The global database of various meteorological and surfacial pa- rameters is maintained at NCEP. This database is generated by taking into consideration the measured values at various worldwide stations and also retrieved from satellite data. The fluxes used in the operational weather forecast models incor- porate in-situ observations through an assimilation process. The main drawback of the data source is the frequent change in assimilation methodology and in model resolution, which has been solved by the re-analysis procedure by NCEP, in- corporating the whole archived data set into a single frozen data assimilation system. The validation and detailed de- scription of the reanalysis of the NCEP SLHF data have been discussed by Kalnay et al. (1996). The daily values of SLHF have been considered for a two months period prior to and after the earthquakes. The mean value during that period has been considered in order to take into account care of the sea- sonal effect. The monthly mean has been subtracted from the daily values to study the anomalous behavior (1SLHF) of SLHF during the earthquakes.

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Analysis of the Low Energy Seismic Activity in the Southern Apulia (Italy)

Analysis of the Low Energy Seismic Activity in the Southern Apulia (Italy)

In all cases both the low number of seismic stations (the average number of polarities per event is 11) and their spatial distribution does not allow to obtain well constrained fault plane solutions. For all the events, the best provided solution (Figure 10 and Table 3) shows for the pressure axis P a trend of about 300˚ and a plunge of about 30˚, whereas the tension T axis has a trend of about 45˚ (NE-SW direction) and a plunge of 20˚. All events reveal strike-slip faulting mechanisms along E-W striking planes and in particular the best constrained mechanism of the 5 May, 2012 earthquake is well repre- sentative of this kind of solution.

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A Modern Method to Improve of Detecting and Categorizing Mechanism for Micro Seismic Events Data Using Boost Learning System

A Modern Method to Improve of Detecting and Categorizing Mechanism for Micro Seismic Events Data Using Boost Learning System

People face a variety of natural disasters in their life such as earthquakes, floods, fires and volcanoes from the past until now (Monadi and et al, 2012; soleymani and et al, 2014) [1][2] . These disasters have impacted human life and imposed irreparable damage on them. It would be possible to reduce the damages and prevent from many more serious damages with correct analysis of seismic events. Various methods are used to forecast the occurrence of earthquake events such as mathematical modeling, ionosphere analysis and studying animals' behavior (Abraham, 2005; Hadjimichael and et al, 2002) [3][4][5]. Some these methods only utilize from a single feature and are not able to use different features in earthquake forecasting. Therefore, earthquake events

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Earthquake Prediction by KIANA Method

Earthquake Prediction by KIANA Method

Earthquake prediction has been one of the earliest desires of the man. Scientists have worked hard to predict earthquakes for a long time. The results of these efforts can generally be divided into two methods of prediction: 1) Statistical Method, and 2) Empirical Method. In the first method, earthquakes are predicted using statistics and probabilities, while the second method utilizes variety of precursors for earthquake prediction. The latter method is time consuming and more costly. However, the result of neither method has fully satisfied the man up to now. In this paper a new method entitled "Kiana Method" is introduced for earthquake prediction. This method offers more accurate results yet lower cost comparing to other conventional methods. In Kiana method the electrical and magnetic precursors are measured in an area. Then, the time and the magnitude of an earthquake in the future is calculated using electrical, and in particular, electrical capacitors formulas. In this method, by daily measurement of electrical resistance in an area we make clear that the area is capable of earthquake occurrence in the future or not. If the result shows a positive sign, then the occurrence time and the magnitude can be estimated by the measured quantities. This paper explains the procedure and details of this prediction method

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Unusual Animal Behaviour before Earthquakes and Multiple Parameter Monitoring in Western Piedmont

Unusual Animal Behaviour before Earthquakes and Multiple Parameter Monitoring in Western Piedmont

A particular tripartite sequence in the vocal alarms of domestic animals and birds was noted: phase A, lasting up to 2 hours, with shrills and high sounds, from 30 minutes until 10 hours before the earthquake, then, when cries stop simultaneously, phase B follows, with a strange and worry silence; finally phase C, with animal cries normally 20-40 seconds before the earthquakes, stopping few seconds before the shock. The phase C is corroborated by the observations of other researchers in case of other earthquakes [8,17-21]. The vocal animal alarms beginning up to 10 hours before local earthquakes, sometimes before distant earthquakes if the future magnitude is great, were contemporaneous to drastic reduction of variations in intensity and declination of the magnetic field and of radioactivity values. So, Figure 5a and b resume an interesting relation between seismic epicentre distances to SPSC, magnitude and percentage of unusual animal behaviours, in relation to domestic animal cries and to bird songs, noted before the same seismic event. Obviously, unusual animal behaviours can be only taken in account for those species which normal behaviour was known.

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Earthquake-triggered landslides in southwest China

Earthquake-triggered landslides in southwest China

Reports and documents of earthquake-triggered landslides in southwest China have been collected from a wide vari- ety of source, there are 835 earthquakes with magnitude 4.7 or greater occurred in the study area according to the latest earthquake statistics. Although the records of strong earth- quakes (M > = 7.0) dates back to 814 BC, data of the oc- currence of landslides in the events is extremely sparse prior to 1500 (Earthquake-resistant and damage prevention depart- ment of State Seismic Bureau, 1995). Limited to the develop- ment level of economy and culture in southwest China in the past time, not every earthquake which triggered landslides had a detailed investigation and records. As a result there is often uncertainty regarding the source parameters of some of the earlier events and, in particular, focal depths are of- ten poorly determined. Not only in China, it is universal that historical earthquake-triggered landslide data is scarce in the world. The first formal and scientific post-earthquake inves- tigation was undertaken following the earthquake swarm in Calabria, Italy in 1783 (Keefer, 2002). Before it, the his- torical accounts of landslides in earthquakes are typically so incomplete and vague that conclusions based on these ac- counts are of limited usefulness (Keefer, 2002). Neverthe-

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Relatively small earthquakes of Javakheti Highland as the precursors of large earthquakes occuring in the Caucasus

Relatively small earthquakes of Javakheti Highland as the precursors of large earthquakes occuring in the Caucasus

Variation of the number of relatively small earthquakes of Javakheti Highland with time is shown in Fig. 2. We used the method of the Creeping Mean for better separation of the anomalies. Namely, we smoothed data series, from 2 to 20 months in length, with a lag of one month until the sharp picture was observed. The 9-month series were found the most appropriate for smoothing, since they proved to be ac- ceptable for further processing and analysing (Comparatively worse graphs were obtained in case of smoothing time series

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Dilatant normal faulting in jointed cohesive rocks: a physical model study

Dilatant normal faulting in jointed cohesive rocks: a physical model study

The rift zone in Iceland shows similar features. Faults of- ten localize along vertical cooling joints, resulting in a planar fault geometry with abrupt changes of fault dip controlled by the depth extent of joints rather than a pure listric shape (An- gelier et al., 1997). This characteristic fault shape could be observed in the grabens of CLNP or in faulted basalts on Hawaii (Holland et al., 2006) and in the presented experi- ments and is more or less independent of the angle between joints and faults. Holland et al. (2006, 2011) propose a con- nectivity of open fractures along faults up to great depths based on field and laboratory observations. Our models sug- gest that this connectivity can be enhanced by the existence of pre-existing vertical joints as they tend to open and con- nect via secondary fractures during faulting.

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Probabilistic Design Earthquake Ground Motions for Nuclear Power Plants Considering Scenario Earthquakes

Probabilistic Design Earthquake Ground Motions for Nuclear Power Plants Considering Scenario Earthquakes

Relatively sufficient information is available for large plate-boundary scenario earthquakes in the subduction zone (Category II). We adopted scenarios of the fault ruptures in the Miyagi-ken Oki earthquakes of a magnitude of 8 class in Category II proposed by the National Research Institute for Earth Science and Disaster Prevention [2]. The National Research Institute for Earth Science and Disaster Prevention [2] assumed scenarios of the fault ruptures in the areas A1, A2, and B [7] shown in Fig. 3 and some combinations of the three areas. The scenarios and the moment magnitudes M W were estimated follows:

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