Aftershocks and the rupture zone of the M S = 8.2, November 15, 2006 Middle Kuril Is. Earthquake and a long-term earthquake forecast for the Kuril-Kamchatka arc for the period from April 2008 to March 2013

Results are reported from the ongoing 2007–2008 work using the method of long-term earthquake prediction for the Kuril-Kamchatka arc based on the patterns of seismic gaps and the seismic cycle. This method was successful in predicting the M _S = 8.2 Simushir I. (Middle Kuril Is.) earthquake occurring in the Simushir I. area on November 15, 2006. An M _S = 8.1 earthquake occurred in the same area on January 13, 2007. We consider the evolution of the seismic process and determine the common rupture region of the two earthquakes. The sequence of M ≥ 6.0 aftershocks and forecasts for these are given. We provide a long-term forecast for the earthquake-generating zone of the Kuril-Kamchatka arc for the next five years, April 2008 to March 2013. Explanations are given for the method of calculation and prediction. The probable locations of future M ≥ 7.7 earthquakes are specified. For all segments of the earthquake-generating zone we predict the expected phases of the seismic cycle, the rate of low-magnitude seismicity (A₁₀), the magnitudes of moderate-sized earthquakes to be expected, with probabilities of 0.8, 0.5, and 0.15, their maximum possible magnitudes, and the probabilities of occurrence of great (M ≥ 7.7) earthquakes. The results of these forecasts are used to enhance seismic safety.     

The long-term earthquake prediction for the Kuril–Kamchatka island arc for the April 2016 through March 2021 period,its modification and application; the Kuril–Kamchatka seismicity before and after the May 24, 2013, M 8.3 deep-focus earthquake in the Sea of Okhotsk

This paper discusses results from ongoing research on long-term earthquake prediction for the Kuril–Kamchatka island arc based on the concepts of seismic gaps and the seismic cycle. We developed a forecast for the next 5 years (April 2016 through March 2021) for all segments of the earthquake-generating zone along the Kuril–Kamchatka arc. The 20 segments of the arc were analyzed to develop forecasts of the appropriate phases of the seismic cycle, a normalized parameter of the rate of small earthquakes (A₁₀), the magnitudes of moderate earthquakes that are expected with probabilities of 0.8, 0.5, and 0.15, the maximum expected magnitudes, and the probabilities of great (M ≥ 7.7) earthquakes. We discuss the seismic process in the Kuril–Kamchatka earthquake-generating zone before and after the deep-focus May 24, 2013 M 8.3 earthquake in the Sea of Okhotsk. The results corroborate the high seismic hazard in the area of Petropavlovsk-Kamchatskii and the urgent need for continuing with and expanding the ongoing work of seismic retrofitting and seismic safety enhancement. We quote practical results from applications of the method during 30 years.     

A Tectonophysical Analysis of Earthquake Frequency—Size Relationship Types for Catastrophic Earthquakes in Central Asia

We performed a tectonophysical analysis of earthquake frequency–size relationship types for large Central Asian earthquakes in the regions of dynamical influence due to major earthquake-generating faults based on data for the last 100 years. We identified four types of frequency–size curves, depending on the presence/absence of characteristic earthquakes and the presence or absence of a downward bend in the tail of the curve. This classification by the shape of the tail in frequency–size relationships correlates well with the values of the maximum observed magnitude. Thus, faults of the first type (there are characteristic earthquakes, but no downward bend) with M_max ≥ 8.0 are classified as posing the highest seismic hazard; faults with characteristic earthquakes and a bend, and with M_max = 7.5–7.9, are treated as rather hazardous; faults of the third type with M_max = 7.1–7.5 are treated as posing potential hazard; and lastly, faults with a bend, without characteristic earthquakes, and with a typical magnitude M_max ≤ 7.0, are classified as involving little hazard. The tail types in frequency–size curves are interpreted using the model of a nonlinear multiplicative cascade. The model can be used to treat different tail types as corresponding to the occurrence/nonoccurrence of nonlinear positive and negative feedback in earthquake rupture zones, with this feedback being responsible for the occurrence of earthquakes with different magnitudes. This interpretation and clustering of earthquake-generating faults by the behavior the tail of the relevant frequency–size plot shows raises the question about the physical mechanisms that underlie this behavior. We think that the occurrence of great earthquakes is related to a decrease in effective strength (viscosity) in the interblock space of faults at a scale appropriate to the rupture zone size.     

A Morphostructural Zoning of the Mountainous Crimea and the Possible Locations of Future Earthquakes

The locations of possible earthquake occurrence (magnitudes M ≥ 6) have been determined for mountainous Crimea and the adjacent sea shelf, including the continental slope zone. The earthquake-generating structures were assumed to be intersections of morphostructural lineaments as found by morphostructural zoning. The measurement of geological and geophysical characteristics was followed by applying a decision rule that was derived previously using the CORA-3 pattern recognition algorithm in order to find possible locations of M ≥ 6 earthquakes in the Caucasus. The results corroborate the high seismic potential for the Yalta area where two events with magnitudes of 6.0 and 6.8 occurred in 1927, as well as indicating the possibility of M ≥ 6 earthquakes in other areas in mountainous Crimea and in the adjacent Black Sea area where no such events have yet been recorded.     

Deep-seated faults and lineaments, and the location of earthquake epicenters in the Russian northeast on land

This paper summarizes the available geological and geophysical material for faults as regards their role in the seismic process. The entirety of the geological and geophysical evidence is used to reveal hidden faults, which are important in influencing the spatial distribution of earthquakes, and to produce a map of the major earthquake-generating faults and lineaments in the Russian northeast. As well as the occurrence of earthquakes at known faults that have surface expression, we find that seismicity tends to occur at the hidden faults and lineaments we have identified, as well as at intersections of faults. We made a quantitative assessment of the relationship of seismicity to tectonic fragmentation of the crust, correlating the density and discordance measure for faults to indicators of seismic activity (rate and energy release of earthquakes per unit area) for the southeast flank of the Okhotsk-Lena seismic region. The results obtained in this study revealed some features in the spatial distribution of earthquakes occurring on land in the Okhotsk-Lena seismic region: the maximum level of seismic activity occurs in areas with moderate values of the discordance measure for faults (12 < ‖D‖ ≤ 18) as identified from gravity data and in zones of increased horizontal gradients of the lines of equal discordance. At these locations, the greatest probability of earthquake occurrence for events of energy class K ≥ 12 corresponds to moderate values of the density of faults visible at the surface (0.12 < τ ≤ 0.16 km^?1).     

Seismic monitoring of source zones of strong earthquakes

A rational choice of the scalar seismic moment and ordering index is proposed that can be advantageously used for the monitoring of source zones of strong earthquakes in order to predict the development of a seismic situation. These parameters are the main characteristics of seismotectonic deformation. The ordering index characterizes a regular change in time of chaotization and ordering phases of the seismic process related to the occurrence of strong aftershocks. Using the December 5, 1997, Kronotskii (M _w = 7.8) and December 26, 2004, Sumatra (M _w = 9.0) earthquakes as an example, temporal variations of the studies parameters in the aftershock zones of these earthquakes are analyzed in detail.     

A long-term earthquake forecast for the Kuril-Kamchatka arc for the period from September 2010 to August 2015 and the reliability of previous forecasts,as well as their applications

We describe results from the ongoing 2008–2010 work on long-term earthquake prediction for the Kuril-Kamchatka arc based on the patterns of seismic gaps and the seismic cycle. We provide a forecast for the next 5 years, September 2010 to August 2015, specified for all segments of the earthquake-generating Kuril-Kamchatka arc zone. For 20 segments we predict the phases of the seismic cycle, the normalized rate of small earthquakes (A₁₀), the magnitudes of moderate earthquakes to be expected with probabilities of 0.8, 0.5, and 0.15, the maximum possible magnitudes, and the probabilities of great (M ≥ 7.7) earthquakes. It is shown that the forecast given for the previous 5 years, from September 2005 to September 2010, was found to be accurate. We report the measures that were taken for seismic safety and retrofitting based on these forecasts.     

Periodic spectral characteristics of seismicity before strong earthquakes and their application

IntroductionMaximumentropyspectralmethod(MEM)(Burg,1972)hadbeenamethodusuallyusedinstudyingtheseismicityanditsmainpurposeistofindthedominantspectrainthelong-termseismicityprocessesinthepastyears(Zhu,1985).Inthispaper,themethodisappliedtostudywhethertherearesomespecialspectraofseismicityinsomespecificstagesinearthquake-generatingprocesses.Sowestudyseparatelythenormalandabnormalstageofearthquakeactivity,whoseactiveprocessisregardedasstablestochasticprocess,inordertofindtheirspectracharactersan…     

A long-term earthquake forecast for the Kuril-Kamchatka arc for the period from September 2011 to August 2016. The likely location,time, and evolution of the next great earthquake with M ≥ 7.7 in Kamchatka

We consider the results from the ongoing 2010–2011 work on long-term earthquake prediction for the Kuril-Kamchatka arc based on the pattern of seismic gaps and the seismic cycle. We develop a forecast for the next 5 years, from September 2011 to August 2016, for all segments of the Kuril-Kamchatka arc earthquake-generating zone. For 20 segments we predict the appropriate phases of the seismic cycle, the normalized rate of small earthquakes (A₁₀), the magnitudes of moderate earthquakes to be expected with probability 0.8, 0.5, and 0.15, and the maximum possible magnitudes and probability of occurrence for great (M ≥ 7.7) earthquakes. This study serves as another confirmation that it is entirely necessary to continue the work in seismic retrofitting in the area of Petropavlovsk-Kamchatskii.     

四川荣县MS4.7、MS4.3、MS4.9地震房屋震害特征和人员伤亡分析

根据四川荣县M_S4.7、M_S4.3、M_S4.9地震现场灾害调查资料,分析房屋震害特征和人员伤亡情况,结果表明震区房屋破坏类型主要为砖混结构、砖木结构和土木结构,其中砖木结构和土木结构受损比较严重,人员伤亡主要由房屋损坏导致;造成此现象的原因主要是该地区房屋建造年代久远,房屋结构不合理、抗震性能差,短时间地震频发造成震害累积,再加上民众防震减灾意识薄弱等。     

Temporary seismological observations in the area of the 2012–2013 Tolbachik Fissure Eruption: Results

The seismicity that accompanied the Tolbachik Fissure Eruption was recorded by additional seismic stations that were installed in the southern Klyuchevskoi Volcanic Cluster area in January to October 2013. We used broadband (0.033–50 Hz) three-component digital Guralp CMG-6TD seismometers. This temporary network provided seismicity data at a lower energy level than can be done using the regional seismograph network of Kamchatka. The processing of the resulting digital records supplied data for compiling a catalog of over 700 M _L = 0–3.5 (K _S = 1.5–8.5) earthquakes, which is an order of magnitude greater than the number of events located by the regional network for the same period of time. The seismicity in the area of Ploskii Tolbachik Volcano was found to concentrate mostly in spatially isolated areas during the eruption. The main isolated clusters of earthquakes were identified both in the eruption area itself and along the periphery of Ploskii Tolbachik Volcano, in the area of the Zimina volcanic massif, and in the Tolud epicenter zone; the eruption zone was not dominant in the seismicity. The region of a shallow seismicity increase beneath Ploskii Tolbachik before the eruption was not found to exhibit any increased activity during the time the temporary seismograph network was operated, which means that a seismicity inversion took place at the beginning of the eruption. We discuss the question of what the earthquake-generating features are that we have identified.     

Seismic performance of bar-mat reinforced-soil retaining wall: Shaking table testing versus numerical analysis with modified kinematic hardening constitutive model

Reinforced-soil retaining structures possess inherent flexibility, and are believed to be insensitive to earthquake shaking. In fact, several such structures have successfully survived destructive earthquakes (Northridge 1994, Kobe 1995, Kocaeli 1999, and Chi-Chi 1999). This paper investigates experimentally and theoretically the seismic performance of a typical bar-mat retaining wall. First, a series of reduced-scale shaking table tests are conducted, using a variety of seismic excitations (real records and artificial multi-cycle motions). Then, the problem is analyzed numerically employing the finite element method. A modified kinematic hardening constitutive model is developed and encoded in ABAQUS through a user-defined subroutine. After calibrating the model parameters through laboratory element testing, the retaining walls are analyzed at model scale, assuming model parameters appropriate for very small confining pressures. After validating the numerical analysis through comparisons with shaking table test results, the problem is re-analyzed at prototype scale assuming model parameters for standard confining pressures. The results of shaking table testing are thus indirectly “converted” (extrapolated) to real scale. It is shown that: (a) for medium intensity motions (typical of M_s≈6 earthquakes) the response is “quasi-elastic”, and the permanent lateral displacement in reality could not exceed a few centimeters; (b) for larger intensity motions (typical of M_s≈6.5–7 earthquakes) bearing the effects of forward rupture directivity or having a large number of strong motion cycles, plastic deformation accumulates and the permanent displacement is of the order of 10–15 cm (at prototype scale); and (c) a large number of strong motion cycles (N>30) of unrealistically large amplitude (A=1.0 g) is required to activate a failure wedge behind the region of reinforced soil. Overall, the performance of the bar-mat reinforced-soil walls investigated in this paper is totally acceptable for realistic levels of seismic excitation.     

Bi-normalized response spectra and seismic intensity in Bucharest for 1986 and 1990 Vrancea seismic events

The Vrancea subcrustal earthquakes of August 30,1986 and May 30,1990 are the two most recent seismic events that have occurred in Romania with moment magnitudes M W ≥ 6.9.The spectral analysis of the strong ground motions recorded in Bucharest reveals that despite small differences in magnitude between the 1986 and 1990 earthquakes,their frequency contents are very different,sometimes even opposing.The main focus of this study is to conduct a comparative analysis of the response spectra in terms of the bi-normalized response spectra(BNRS) proposed by Xu and Xie(2004 and 2007) for strong ground motions recorded in Bucharest during these two seismic events.The mean absolute acceleration and relative velocity response spectra for the two earthquakes are discussed and compared.Furthermore,the mean bi-normalized absolute acceleration and normalized relative velocity response spectra with respect to the control period T C are computed for the ground motions recorded in Bucharest in 1986 and 1990.The predominant period T P is also used in this study for the normalization of the spectral period axis.Subsequently,the methodology proposed by Martinez-Perreira and Bommer(1998) is applied in order to estimate the seismic intensity of the two events.The results are discussed and several conclusions regarding the possibility of using the bi-normalized response spectra(BNRS) are given.     

京津唐地区地震转换波测深结果

1975—1979年间在京津唐地区完成了八条地震转换波测深的剖面工作,本文介绍所取得的主要成果。结果表明转换波法用于地壳、上地幔深部结构的探测是有效的。深部构造剖面与震源分布的对比表明,本区几乎所有强震震源都分布在“花岗岩”层的某些特殊部位上。唐山和马坊大震地区的深部构造具有相似的特征,这就是“花岗岩”层的相对隆起,上地幔界面的强烈凹陷,岩石圈相应地急剧增厚以及存在深大断裂     

Shifting Correlation Between Earthquakes and Electromagnetic Signals: A Case Study of the 2013 Minxian–Zhangxian ML 6.5 (MW 6.1) Earthquake in Gansu,China

The shifting correlation method (SCM) is proposed for statistical analysis of the correlation between earthquake sequences and electromagnetic signal sequences. In this method, the two different sequences were treated in units of 1 day. With the earthquake sequences fixed, the electromagnetic sequences were continuously shifted on the time axis, and the linear correlation coefficients between the two were calculated. In this way, the frequency and temporal distribution characteristics of potential seismic electromagnetic signals in the pre, co, and post-seismic stages were analyzed. In the work discussed in this paper, we first verified the effectiveness of the SCM and found it could accurately identify indistinct related signals by use of sufficient samples of synthetic data. Then, as a case study, the method was used for analysis of electromagnetic monitoring data from the Minxian–Zhangxian M_L 6.5 (M_W 6.1) earthquake. The results showed: (1) there seems to be a strong correlation between earthquakes and electromagnetic signals at different frequency in the pre, co, and post-seismic stages, with correlation coefficients in the range 0.4–0.7. The correlation was positive and negative before and after the earthquakes, respectively. (2) The electromagnetic signals related to the earthquakes might appear 23 days before and last for 10 days after the shocks. (3) To some extent, the occurrence time and frequency band of seismic electromagnetic signals are different at different stations. We inferred that the differences were related to resistivity, active tectonics, and seismogenic structure.     

松原地区群体建筑结构地震响应及抗震韧性分析

近年来吉林省松原地区破坏性地震频发,十分必要对当地群体建筑结构的抗震韧性进行分析。对吉林省松原地区的群体建筑结构进行地震响应分析以及抗震韧性评估,对比分析城市和乡镇群体建筑结构在地震作用下的地震响应和抗震韧性。根据《建筑抗震韧性评价标准(GBT 38591—2020)》确定群体建筑结构抗震韧性评估流程,通过韧性指数法和韧性等级法对群体建筑结构的抗震韧性进行定量分析,对城乡抗震韧性的评价结果为当地防震减灾提供理论支持。     

四川芦山7.0级地震前中小地震P轴方位角CV值的变化

通过对2003年1月1日—2013年4月1日芦山地震前震源区中小地震震源机制解的分析,发现不同阶段的震源机制解在一定程度上反映了强震孕育过程中构造应力场随时间的变化。震源区中小地震的P轴方位角C_V值在芦山M7.0地震发生前有一个上升-下降-上升的过程,只是相比于汶川8.0级地震前C_V值的下降-上升过程经历了更长的时间,这表明四川芦山M7.0地震的孕育经历了长时间的应力积累,与许多研究结果相一致。2007年1月1日—2014年4月1日C_V值空间分布的非均匀性特征在龙门山断裂带南段有显著的增强与减弱过程,对于发震地点可能有一定的指示意义。     

Seismic characteristics near the epicenter of the 1303 Hongtong <Emphasis Type="Italic">M</Emphasis>=8 earthquake,Shanxi Province and its implication

In this paper, we calculated the seismic pattern of instrumental recorded small and moderate earthquakes near the epicenter of the 1303 Hongtong M=8 earthquake, Shanxi Province. According to the spatial distribution of small and moderate earthquakes, 6 seismic dense zones are delineated. Temporal distribution of M _L≥2 earthquakes since 1970 in each seismic dense zone has been analyzed. Based on temporal distribution characteristics and historical earthquake activity, three types of seismicities are proposed. The relationship between seismic types and crustal medium is analyzed. The mechanism of three types is discussed. Finity of strong earthquake recurrence is proposed. Seismic hazard in mid-long term and diversity of earthquake disaster in Shanxi seismic belt are discussed.     

Archeoseismological study in Salachik,the ancient capital of Crimean Khans

Archeological, archeoseismological, and seismotectonic studies were carried out in Salachik, the ancient capital of the Crimean Khans, on the outskirts of the modern city of Bakhchysarai, Crimea. The following damage and deformations of medieval buildings were observed: tilted building walls, shifted elements of building structures, rotation of fragments of walls and building blocks around the vertical axis, considerable deformations of arch structures, and fissures running through several rows of building blocks. These deformations are of a seismogenic nature. Traces of at least two strong ancient earthquakes were revealed in the medieval monuments of Salachik. Based on analysis of kinematic indicators, it is found that the maximum seismic intensity (VIII ≤ I ₀ ≤ IX points) was due to an earthquake occurred in the west. Based on historical seismologic data, one of the two earthquakes is dated by April 30, 1698. Also, structural damage to buildings in Salachik was caused by Crimean earthquakes in 1927. The findings can be used for a comprehensive assessment of seismic hazards on the Crimean Peninsula.