Earthquake probabilities and magnitude distribution (<Emphasis Type="Italic">M</Emphasis>≥6.7) along the Haiyuan fault,northwestern China

In recent years, some researchers have studied the paleoearthquake along the Haiyuan fault and revealed a lot of paleoearthquake events. All available information allows more reliable analysis of earthquake recurrence interval and earthquake rupture patterns along the Haiyuan fault. Based on this paleoseismological information, the recurrence probability and magnitude distribution for M≥6.7 earthquakes in future 100 years along the Haiyuan fault can be obtained through weighted computation by using Poisson and Brownian passage time models and considering different rupture patterns. The result shows that the recurrence probability of M _S≥6.7 earthquakes is about 0.035 in future 100 years along the Haiyuan fault.     

Characteristics of fault rocks and paleo-earthquake source along the Koktokay-Ertai fault zone,Xinjiang,China

ＣｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｆａｕｌｔｒｏｃｋｓａｎｄｐａｌｅｏｅａｒｔｈｑｕａｋｅｓｏｕｒｃｅａｌｏｎｇｔｈｅＫｏｋｔｏｋａｙＥｒｔａｉｆａｕｌｔｚｏｎｅ，Ｘｉｎｊｉａｎｇ，ＣｈｉｎａＬＡＮＢＩＮＳＨＩ１）（史兰斌）ＣＨＵＡＮＹＯＮ...     

Earthquake triggering and delaying caused by fault interaction on Xianshuihe fault belt,southwestern China

The coseismic Coulomb stress change caused by fault interaction and its influences on the triggering and delaying of earthquake are briefly discussed.The Xianshuihe fault belt consists of Luhuo,Daofu,Kangding,Qianning and Ganzi fault.Luohuo(Ms=7.6,1973)-Kangding(Ms=6.2,1975)-Daofu(Ms=6.9,1981)-Ms=6.0,1982)earthquake is a seismic sequence continuous on the time axis with magnitude greater than6.0.They occurred on the Luhuo.Kangding,Daofu and Ganzi fault,respectively.The coseismic Coulomb stress changes caused by each earthquake on its surrounding major faults and microcracks are calculated,and their effects on the triggering and delaying of the next earthquake and aftershocks are analyzed.It is shown that each earthquake of the sequence occurred on the fault segment with coseismic Coulomb stress increases caused by its predecessors,and most after-shocks are distributed along the microcracks with relatively larger coseismic Coulomb stress increases resulted from the main shock.With the fault interaction considered,the seismic potential of each segment along Xianshuihe fault belt is reassessed,and contrasted with those predicted results ignoring coseismic Coulomb stress change,the significance of fault interaction and its effect on triggering and delaying of earthquake are emphasized.It is con-cluded that fault interaction plays a very important role on seismic potential of Xianshuihe fault belt,and the maximal change of future earthquake probability on fault segment is up to 30.5%.     

Study on Active Faults and Seismogenic Structure for the 1989 Batang M6.2 ～ 6.7 Earthquake Swarm in the Litang-Batang Region of West Sichuan, China

INTRODUCTIONGeological investigations since the1970s have shown that the sub_longitudinal Jinshajiang andHonghe(Red River)fault zones constitutethe western boundary of“Rhombic Sichuan_Yunnan Block”onthe Sichuan_Tibet border and display mainly dextral sh…     

The Rhythm of Earthquake Activity and an Analysis on the Earthquake Tendency of the World, the Chinese Continent and North China

Based on the Morlet complex wavelet transformation, the authors put forward a kind of new method for distinguishing periods of seismic activity and quietude and a new physical thought on the time-dependent wavelet accumulation energy spectrum with periods, the time-frequency distribution of wavelet vibration period spectrum and period-specific wavelet vibration spectrum. By applying the above methods to a time series which is composed of earthquake accumulation energy per year for the world, the Chinese continent and North China,respectively, we obtained some new information about the rhythm of shallow earthquake activity. Considering the historic earthquakes and the rhythm characteristics of current strong earthquake activity, the earthquake tendency in the next years is discussed.     

Deep structural characteristics and seismogenesis of the M≥8.0 earthquakes in North China

Introduction North China is a seismically active area in the eastern part of China, where four M8.0 earthquakes have been recorded in the historical documents and confirmed by the researchers. The first is the M=8.0 earthquake occurred in A.D. 1303 in Hongtong, Shanxi Province. It was the ear-liest M=8.0 earthquake recorded in the historical document in China. The second is the M=8.0 earthquake occurred in A.D. 1556 in Huaxian County, Shaanxi Province. The other two are the M=8.5 earth…     

Assessment of the Seismic Situation in the Region of Greece’s Eastern Coast of the Aegean Sea before the Earthquake with M = 6.7 (October 30, 2020)

Izvestiya, Physics of the Solid Earth - Abstract—A detailed study has been carried out regarding temporal variations of seismicity in the region of Greece’s eastern coast of the Aegean...     

Progress in Earthquake Science and Technology in China: Review and Prospects (I)

ＩＮＴＲＯＤＵＣＴＩＯＮＩｔｉｓｋｎｏｗｎｔｈａｔＣｈｉｎａｉｓａｎｅａｒｔｈｑｕａｋｅ ｐｒｏｎｅｃｏｕｎｔｒｙｉｎｔｈｅｗｏｒｌｄａｎｄｉｓａｌｓｏａｃｏｕｎｔｒｙｓｕｆｆｅｒｉｎｇｍｏｓｔｓｅｖｅｒｅｓｅｉｓｍｉｃｃａｌａｍｉｔｉｅｓｉｎｔｈｅｗｏｒｌｄ .Ｃｈｉｎａ’ｓｔｅｒｒｉｔｏｒｙｏｃｃｕｐｉｅｓａｂｏｕｔ 1 1 4ｏｆｔｈｅｇｌｏｂａｌｃｏｎｔｉ ｎｅｎｔａｌａｒｅａ ,ｗｈｉｌｅａｂｏｕｔ 1 3ｏｆｇｌｏｂａｌＭ≥ 7.0ｃｏｎｔｉｎｅｎｔａｌｅａｒｔｈｑｕａｋｅｓｏｃｃｕｒｒｅｄｉｎＣｈ…     

Progress in Earthquake Science and Technology in China: Review and Prospects (Ⅰ)

In the article the author looks back the hard development course and great progress in earth quake science and technology in China during the last near a half of century and expounds the following 3 aspects: (1) The strong desire of the whole society to mitigate seismic disasters and reduce the effect of earthquakes on social-economic live is a great driving force to push forward the development of earthquake science and technology in China; (2) To better ensure people‘ s life and property, sustainable economic development, and social stability is an essential purpose to drive the development of earthquake science and technology in China; and (3) To insist on the dialectical connection of setup of technical system for seismic monitoring with the scientific research of earthquakes and to better handle the relation between crucial task, current scientif ic level, and the feasibility are the important principles to advance the earthquake science and technology in China. Some success and many setbacks in earthquake disaster mitigation consistently enrich our knowledge regarding the complexity of the conditions for earthquake occurrence and the process of earthquake preparation, promote the reconstruction and modernization of technical system for earthquake monitoring, and deepen the scientific research of earthquakes. During the last 5 years, the improvement and modernization of technical system for earthquake monitoring have clearly provided the technical support to study and practice of earthquake prediction and pre caution, give prominence to key problems and broaden the field of scientific research of earth quakes. These have enabled us to get some new recognition of the conditions for earthquake oc currence and process of earthquake preparation, characteristics of seismic disaster, and mecha nism for earthquake generation in China‘s continent. The progress we have made not only en courages us to enhance the effectiveness of earthquake disaster mitigation, but also provides a basis for accelerating further development of earthquake science and technology in China in the new century, especially in the 10th five-year plan. Based on the history reviewed, the author sets forth a general requirement for develop ment of earthquake science and technology in China and brings out 10 aspects to be stressed and strengthened at present and in the future. These are: upgrade and setup of the network of digitized seismic observation; upgrade and setup of the network for observation of seismic pre cursors; setup of the network for observation of strong motion; setup of the laboratories for ex periment on seismic regime; establishment of technical system for seismic information, emer gency command and urgent rescue; research on short-term and imminent earthquake predic tion; research on intermediate- and long-term earthquake prediction; research on attenuation of seismic ground motion, mechanism for seismic disaster, and control on seismic disaster; ba sic research fields related to seismology and geoscience. We expect that these efforts will signifi cantly elevate the level of earthquake science and technology in China to the advanced interna tional level, improve theories, techniques, and methods for earthquake precaution and predic tion, and enhance the effectiveness of earthquake disaster mitigation.     

Earthquake Research in China General Contents,Vol.14(2000)

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Deep structural characteristics and seismo—genesis of the M≥8.0 earthquakes in North China

Based on the results from seismogeological study,aeromagnetic inversion and deepseismic sounding(DSS),it is found that the M≥8.0 earthquakes in North China have three common deep structural characteristics,i.e,they all took place above the ultra-crustal deep faults or on the edges of the tectonic blocks with higher intensity,and there are low-velocity,low-density and high-conductive layers deep in the epicentral regions.The origins of the earth-quakes are also discussed and the two possibilities of seismogenesis are proposed,i.e,tectonic movement and intracrustal explosion.     

Flow Characteristics of Large-Scale Liquefaction-Slip of the Loess Strata in Shibei Tableland, Guyuan City, Induced by the 1920 Haiyuan M8 1/2 Earthquake

Based on the dynamic triaxial liquefaction test of the loess samples which are taken from Shibei tableland, Guyuan City, Ningxia, China, the characteristics of dynamic strain, dynamic stress and pore water pressure are studied under cyclic loading. Triaxial shear test is conducted immediately after the sample reaches liquefaction point. During the test, the property of the liquefied soil is analyzed through fluid mechanics method, whereby the fluidity of the liquefied soil is represented by apparent viscosity.The results show that the fluidity of liquefied loess changes from "shear thickening" to "shear thinning" as the shear force continues, and the fluidity of liquefied loess is closely related to its structure. In addition, in the process of forming a new stable state, the apparent viscosity and deviant stress change with axial strain in a similar approach. When the sample reaches its stable state, it meanwhile shows a relatively stable apparent viscosity. According to the fluid mechanics and the law of conservation of energy, the slip distance of the liquefied soil is estimated, and the results are in good agreement with the field investigation results.     

Properties of the Aftershock Sequences of the 2003 Bingöl, M D = 6.4, (Turkey) Earthquake

Aftershock sequences of the magnitude M _{W =}6.4 Bingöl earthquake of 1 May, 2003 (Turkey) are studied to analyze the spatial and temporal variability of seismicity parameters of the b value of the frequency-magnitude distribution and the p value describing the temporal decay rate of aftershocks. The catalog taken from the KOERI contains 516 events and one month’s time interval. The b value is found as 1.49 ± 0.07 with Mc =3.2. Considering the error limits, b value is very close to the maximum b value stated in the literature. This larger value may be caused by the paucity of the larger aftershocks with magnitude M _D ≥ 5.0. Also, the aftershock area is divided into four parts in order to detect the differences in b value and the changes illustrate the heterogeneity of the aftershock region. The p value is calculated as 0.86 ± 0.11, relatively small. This small p value may be a result of the slow decay rate of the aftershock activity and the small number of aftershocks. For the fitting of a suitable model and estimation of correct values of decay parameters, the sequence is also modeled as a background seismicty rate model. Constant background activity does not appear to be important during the first month of the Bingöl aftershock sequences and this result is coherent with an average estimation of pre-existing seismicity. The results show that usage of simple modified Omori law is reasonable for the analysis. The spatial variability in b value is between 1.2 and 1.8 and p value varies from 0.6 to 1.2. Although the physical interpretation of the spatial variability of these seismicity parameters is not straightforward, the variation of b and p values can be related to the stress and slip distribution after the mainshock, respectively. The lower b values are observed in the high stress regions and to a certain extent, the largest b values are related to Holocene alluvium. The larger p values are found in some part of the aftershock area although no slip occurred after the main shock and it is interpreted that this situation may be caused by the alluvium structure of the region. These results indicate that the spatial distribution in b and p values are generally related to the rupture mechanism and material properties of an aftershock area.     

Provenance,depositional process,and tectonic setting of gold placer from the Bétaré-Oya Gold District(East-Cameroon,Central Africa)along the Precambrian Sanaga fault

The Bétaré-Oya Gold District is one of the three gold districts in East Cameroon with varied types of mining. The study site is an open-cast mine located in an alluvial plain. The strata succession globally consists of two positive sequences represented by three facies associations and seven lithofacies: massive clast-supported(Gcm), massive trough-cross bedded(Gtm), and massive matrix-supported(Gmm)conglomerates; massive sands(Sm); and massive(Fm), heterolothic(Fhl), and convolute and heterolit...     

Earthquake magnitude estimation using the τ c and P d method for earthquake early warning systems

Earthquake early warning (EEW) systems are one of the most effective ways to reduce earthquake disaster. Earthquake magnitude estimation is one of the most important and also the most difficult parts of the entire EEW system. In this paper, based on 142 earthquake events and 253 seismic records that were recorded by the KiK-net in Japan, and aftershocks of the large Wenchuan earthquake in Sichuan, we obtained earthquake magnitude estimation relationships using the τ _c and P _d methods. The standard variances of magnitude calculation of these two formulas are ±0.65 and ±0.56, respectively. The P _d value can also be used to estimate the peak ground motion of velocity, then warning information can be released to the public rapidly, according to the estimation results. In order to insure the stability and reliability of magnitude estimation results, we propose a compatibility test according to the natures of these two parameters. The reliability of the early warning information is significantly improved though this test.     

Strong (M ≥ 7.0) Earthquake-Prone Areas in Hellenides,Greece

Izvestiya, Physics of the Solid Earth - Geological and geomorphological criteria for the areas prone to the earthquakes with magnitudes M ≥ 7.0 are determined for the territory of the...     

Earthquake Research in China General Contents,Vol.1 6(2002)

Ｎｏ .1ＰｒｏｇｒｅｓｓｉｎＥａｒｔｈｑｕａｋｅＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙｉｎＣｈｉｎａ :ＲｅｖｉｅｗａｎｄＰｒｏｓｐｅｃｔ (ＩＩ)ＣｈｅｎＺｈａｎｇｌｉ ( 1 )……………………………………………………………………………ＳｃａｌｉｎｇｏｆＲｅｄｕｃｅｄＥｎｅｒｇｙｏｒＡｐｐａｒｅｎｔＳｔｒｅｓｓａｎｄＩｔｓＳｅｉｓｍｏｌｏｇｉｃａｌＳｉｇｎｉｆｉｃａｎｃｅＷｕＺｈｏｎｇｌｉａｎｇ ( 2 0 )…………………………………………………………………………Ｒｅｓｅａｒｃｈｏｎｔｈｅ 3 ＤＳｅｉｓｍｉ…     

Faulting on the Anninghe fault zone, Southwest China in Late Quaternary and its movement model

The Anninghe fault is one of the significant earthquake-generating fault zones in the Southwest China. Local his-torical record shows that a M≥7 strong earthquake occurred in the year of 1536. On the basis of the detailed air-photographic interpretation and field investigation, we have acquired the following knowledge: 1 The average sinistral strike-slip rate since the Late Pleistocene is about 3~7 mm/a; 2 There is important reverse faulting along the fault zone besides the main left-lateral strike-slip motion, and the shortening rate across the Anninghe fault zone due to the reverse faulting is about 1.7~4.0 mm/a. If the Xianshuihe fault zone is simply partitioned into the Anninghe and Daliangshan faults, we can also get a slip rate of 3~7 mm/a along the Daliangshan fault zone, which is the same as that on the Anninghe fault zone. Moreover, on the basis of our field investigation and the latest knowledge concerning the active tectonics of Tibetan crust, we create a dynamic model for the Anninghe fault zone.