Completeness Analysis of the Historical Earthquake Catalogue in China

The historical earthquake catalogue of China has lasted more than 3000 years,and most of its data are inferred from historical records.The earthquake catalogue in earlier times is not complete owing to various reasons,so some events are lost.This paper estimates the loss rate of earthquakes with various magnitudes in the historical earthquake catalogue for different time intervals quantitatively by using the Gutenberg-Richter formula and modern instrumental records,which will provide the references for statistic research in seismicity.     

Overview of Earthquake Preparedness and Disaster Mitigation in China

As an earthquake-prone country, China has made sustained efforts in the study of earthquakes and disaster mitigation during the past several decades, with China Seismological Bureau (CSB) as the backbone of these efforts. Working towards this purpose, a series of key projects were implemented in the “Ninth Five-Year Plan” (1995-2000) to upgrade earthquake monitoring systems and to improve the supporting infrastructure, significant results in earthquake science were achieved. In the new century, we have worked out a blueprint for earthquake preparedness and disaster mitigation in the “Tenth Five-Year Plan”, which emphases 3 systems (i.e. Seismic Monitoring & Prediction, Seismic Hazards Prevention, Emergency Response), and 10 key projects in earthquake science and technology.     

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.     

Calculation of Calibration Functions and Explosive Aftershock Magnitudes in the Near Field

The current calibration function used in calculating the magnitude of natural earthquakes within 5km is a constant; a fact that causes several serious difficulties for the calculation of the magnitude of small and shallow-focus earthquakes. According to the attenuation law of explosions and the propagation theory of elastic waves, the calibration function is calculated for near field quakes from 0kin to 5kin. Magnitudes of two aftershock sequences are calculated. The magnitudes of most explosion earthquakes are small, ranging mainly from magnitude -0.5 to 1.0. The M-t chart of the explosive aftershocks is completely different from that of strong earthquake aftershocks. It not only shows positive columnar lines indieatJng large magnitudes but also short negative columnar lines indicating small magnitudes.     

Analysis of recent changes in rainfall and drought indices in Nigeria, 1981–2015

ABSTRACT

This study assesses the climate change impact on rainfall and drought incidents across Nigeria. Linear regression, Mann-Kendall tests and lag-1 serial correlation were adopted to analyse the trends and variability of rainfall and drought at 18 synoptic stations. Analysis of annual precipitation series indicates an increase in rainfall amounts at all stations, except Minna, Gusau and Yola. Seventeen of the 18 stations recorded at least one main drought period, between 1983 and 1987. A decreasing trend for the standardized precipitation index SPI-12 series was seen at Yola station, while the other stations showed an increasing trend. Also, Nigeria witnessed more annual rainfall totals but with high variability within the rainy months of the year in the first 15 years of the 21st century compared to the 20th century. Such variability in rainfall may have a significant effect on groundwater resources and the hydrology of Nigeria.     

The Characteristic Analysis and Seismic Triggering Study of the M6.2 and M6.1 Dayao Earthquake Sequences in 2003

INTRODUCTIONTheM6·2 andM6·1 earthquakes occurred successivelyin Dayao,Yunnan Province on July 21and October 16 ,2003 and bothinduced human casualty and economic loss to some extent .Adequatehistorical information reveals that ,earthquakes bigger thanM6·0 in Yunnan are distributed mainlyalong some active tectonic faults and seismic belts . Dayao and Yao an are in the Dianzhong tectonicblock andthere are noapparentfaultsthere(Su Youjing,2004) .Seismic activitylevel inthisregioniswea…     

Correlation between movement of tectonicblocks and earthquakes in groups

Introduction ZHANG and ZHONG (1977), ZHANG, et al (1978) and ZHANG (1984) pointed out that Chinese mainland is divided into two parts by the NS-trending tectonic belt, i.e., the eastern area and the western area, and each area is divided into tectonic blocks by faults. In the eastern area, the faults are trending NNE and NNW, mainly NNE, and the long axis strike of blocks is nearly trending NS. In the western area, faults are trending NEE and NWW, mainly NWW, long axis strike …     

Lévy Gradient Descent: Augmented Random Search for Geophysical Inverse Problems

Surveys in Geophysics - A new efficient random search algorithm is introduced for solving inversion problems in geophysical studies. The proposed algorithm is inherently a stochastic optimization...     

Examination of Historical Data of the 1125 Lanzhou M7.0 Earthquake and Analysis of Seismogenic Structure

Detailed examination of historical data of earthquakes and field investigations of loess landslide caused by the earthquake and tracing of active faults in Lanzhou area indicate that the Yijitanpu town,one of six towns of Jincheng city,was devastated by the 1125 Lanzhou earthquake.The citly is now located in the Vinylon Factory south of Hekou(River Mouth)in the Xigu distict of Lanzhou city.We delermined that the six old towns mentioned in historical records lie in an area stretching from the south of Xigu district to Hekou in Lanzhou.This is consistent with the distibution of loess landslides caused by the earthquake,the extension of Holocene active faults,and the distribution of traces of the seismic rupture zone.A comprehensive analysis shows that the seismogenic structure for the 1125 Lanzhou M7.0 earthquake should be the Xianshuigou fault segment at the western termination of the north-border active fault zone of the Maxianshan Mountains which are located in south of Lanzhou city with the distance of only 4km.     

Characteristics and Implication of the Earthquake Swarm Occurred in Fuzhou in September 1999

on Septmeber 23,1999,an earthquake swarm occured in Fuzhou,Because the swarm occurred in the region where earthquaks occurred scarcely before and very close to the center of the city as well as shortly after the Jiji earthquake with Ms7.6 in Taiwan,September 21,1999,has aroused interest broadly.In this paper,we analyzed the characteristics of spatial and temporal distribution of the earthquake swarm and validated magnitude-number constituent of the swarm is special.In present theory,the earthquake swarm means that a small scale macro original rupture has formed in the layer of the crust in Fuzhou region where moderately strong earthquake risk exists.     

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.     

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…     

Visibility Graph Analysis of the 2003–2012 Earthquake Sequence in the Kachchh Region of Western India

A visibility graph (VG) is a rather novel statistical method in earthquake sequence analysis; it maps a time series into networks or graphs, converting dynamical properties of the time series into topological properties of networks. By using the VG approach, we defined the parameter window mean interval connectivity time <T_c>, that informs about the mean linkage time between earthquakes. We analysed the time variation of <T_c> in the aftershock-depleted catalogue of Kachchh Gujarat (Western India) seismicity from 2003 to 2012, and we found that <T_c>: i) changes through time, indicating that the topological properties of the earthquake network are not stationary; and, ii) appeared to significantly decrease before the largest shock (M5.7) that occurred on March 7, 2006 near the Gedi fault, an active fault in the Kachchh region.     

Magnitudes and time distribution of the swarm earthquakes August–November 2000 in NW Bohemia

During the earthquake swarm in the north-western part of the Czech Republic which happened between August and November 2000 more than 10 500 single events have been recorded at the station Wernitzgruen (WERN), located in the Vogtland (Germany) at about 13 km hypocentral distance. Most of the events were weak and followed each other so closely in time that they could not be identified at more distant stations in Middle Europe. A procedure to determine magnitudes of very small events from recordings in short distances is realized and discussed. The development over time of the seismic activity shows the typical pattern of previous earthquake swarms in this region consisting of multiple swarm episodes. For the first time, however, it is analysed using the time intervals between successive events. However, no new and reproducible patterns were found which could be useful for prognostics of future swarm activities.     

The Characteristics of Earthquake Disasters and Countermeasures for Their Mitigation in Metropolitans

Metropolitans are a result of fast economic development in China. Many metropolitans have emerged in the eastern part of China. Earthquake disasters in metropolitans are more complicated and serious than those in a smaller city, and the impact of earthquake disaster on the economy and society is large. The characteristics of earthquake disasters and countermeasures to protect against and mitigate disaster in the metropolitan, as well as some key research fields in the earthquake disaster protection and mitigation, are discussed.     

Intensity Distribution of Jingtai Ms 6.2 Earthquake in 1990 and Causative Fault

A Ms 6.2 strong earthquake occurred at 16:07 on October 20,1990 in a juncture of the three counties of Jingtai,Tianzhu,Gulang in Gansu Province.Field observations indicate that the macroseismic epicenter lies from Xiatang to Daquanwan and that its geographical location is at 37°07'N and 103°37.5'E.The epicentral intensity is Ⅷ degree.The meizoseismal region,covering about 20 km-,is an elliptical area with its long axis orienting NWW.In the circled areas with the earthquake intensity from VI to Ⅷ degree,the formation cause of high intensity(Ⅷ)anomalous area appeared in the Ⅶ area has been discussed in this paper.According to the data of direct aftershock area,epicentrai intensity area,focal mechanism solution and the direction of the ground motion,etc.,this strong earthquake was caused by latest sinistral lateral movement of Laohushan fault that has been the most active fault since the Holocene.     

Analysis and interpretation of the seismic response of RC buildings in Concepción during the February 27, 2010, Chile earthquake

Observed trends in the seismic performance of eight severely damaged reinforced concrete (RC) structures after the February 27, 2010, Chile earthquake are presented in this article. After a reconnaissance and surveying process conducted immediately after the earthquake, several aspects not conventionally considered in building design were observed in the field. Most of the considered structures showed extensive localized damage in walls of lower stories and first basements. Several factors indicate that damage was brittle, and occurred mainly in recent RC structures supported on soft soils with some degree of vertical and/or horizontal irregularity. Non-ductile behavior has been inferred due to the lack of evidence of spread damage in the structure, and the fact that very similar structural configurations existed nearby without apparent damage. Some key aspects in understanding the observed damage are: geographical orientation of the building, presence of vertical and horizontal irregularities, wall thickness and reinforcement detailing, and lack of sources for energy dissipation. Additionally, results of a building-code type analysis are presented for the 4 most critical buildings, and Demand/Capacity ratios are calculated and compared with the observed behavior. It is concluded that the design codes must be revised relative to wall design provisions.