Crustal structure beneath the Songpan—Garze orogenic belt

The Benzilan-Tangke deepseismic sounding profile in the western Sichuan region passes through the Song-pan-Garze orogenic belt with trend of NNE.Based on the travel times and the related amplitudes of phases in the record sections,the 2-D P-wave crustal structure was ascertained in this paper.The velocity structure has quite strong lateral variation along the profile.The crust is divided into 5layers,where the first,second and third layer belong to the upper crust,the forth and fifth layer belong to the lower crust.The low velocity anomaly zone gener-ally exists in the central part of the upper crust on the profile,and it integrates into the overlying low velocity basement in the area to the north of Ma‘erkang.The crustal structure in the section can be divided into 4parts:in the south of Garze-litang fault,between Garze-Litang fault and Xianshuihe fault,between Xianshuihe fault and Longriba fault and in the north of Longriba fault,which are basically coincided with the regional tectonics division.The crustal thickness decreases from southwest to northeast along the profile,that is ,from62km in the region of the Jinshajiang River to 52km in the region of the Yellow River.The Moho discontinuity does not obviously change across the Xianshuihe fault basesd on the PmP phase analysis.The crustal average velocity along the profile is lower,about 6.30 km/s.The Benzilan-Tangke profile reveals that the crust in the study area is orogenic.The Xianshuihe fault belt is located in the central part of the profile,and the velocity is positive anomaly on the upper crust,and negative anomaly on the lower crust and upper mantle.It is considered as a deep tectonhic setting in favor of strong earthquake‘s accumulation and occurrence.     

Effect of asymmetry and irregularity of seismic waves on earthquake-induced differential settlement of buildings on natural subsoil

The effect of asymmetry and irregularity of the inputted seismic waves on the earthquake-induced differential settlement of the buildings on natural subsoil is investigated in terms of the earthquake damage phenomena, theoretical analyses, dynamic triaxial tests and shaking table tests. A conclusion can be drawn from the investigation results that, the asymmetrical and irregular character of the inputted seismic waves themselves may have a significant contribution to the differential settlement of subsoil and buildings in some cases, and this is a necessary factor to be considered in reasonable evaluation for the differential settlement and other problems relating to the soil deformation due to earthquakes.     

Morphological analysis of active Mount Nemrut stratovolcano, eastern Turkey: evidences and possible impact areas of future eruption

Mount Nemrut, an active stratovolcano in eastern Turkey, is a great danger for its vicinity. The volcano possesses a summit caldera which cuts the volcano into two stages, i.e. pre- and post-caldera. Wisps of smoke and hot springs are to be found within the caldera. Although the last recorded volcanic activity is known to have been in 1441, we consider here that the last eruption of Nemrut occurred more recently, probably just before 1597. The present active tectonic regime, historical eruptions, occurrence of mantle-derived magmatic gases and the fumarole and hot spring activities on the caldera floor make Nemrut Volcano a real danger for its vicinity. According to the volcanological past of Nemrut, the styles of expected eruptions are well-focused on two types: (1) occurrence of water within the caldera leads to phreatomagmatic (highly energetic) eruptions, subsequently followed by lava extrusions, and (2) effusions–extrusions (non-explosive or weakly energetic eruptions) on the flanks from fissures. To predict the impact area of future eruptions, a series of morphological analyses based on field observations, Digital Elevation Model and satellite images were realized. Twenty-two valleys (main transport pathways) were classified according to their importance, and the physical parameters related to the valleys were determined. The slope values in each point of the flanks and the Heim parameters H/L were calculated. In the light of morphological analysis the possible impact areas around the volcano and danger zones were proposed. The possible transport pathways of the products of expected volcanic events are unified in three main directions: Bitlis, Guroymak, Tatvan and Ahlat cities, the about 135 000 inhabitants of which could be threatened by future eruptions of this poorly known and unsurveyed volcano.     

An Mw based earthquake Catalogue for central, northern and northwestern Europe using a hierarchy of magnitude conversions

Data from 25 local catalogues and 30special studies of earthquakes in central,northern and northwestern Europe have beenincorporated into a Databank. The dataprocessing includes discriminating eventtypes, eliminating fake events and dupletsand converting different magnitudes andintensities to M_w if this is not givenby the original source. The magnitudeconversion is a key task of the study andimplies establishment of regressionequations where no local relations exist.The Catalogue contains tectonic events fromthe Databank within the area44°N–72°N,25°W–32°E and the time period1300–1993. The lower magnitude level forthe Catalogue entries is setat M_w == 3.50. The area covered by thedifferent catalogues are associated withpolygons. Within each polygon only datafrom one or a small number of the localcatalogues, supplemented by data fromspecial studies, enter the Catalogue. Ifthere are two or more such catalogues orstudies providing a solution for an event,a priority algorithm selects one entry forthe Catalogue. Then M_w is calculatedfrom one of the magnitude types, or frommacroseismic data, given by the selectedentry according to another priority scheme.The origin time, location, M_w magnitude and reference are specified for eachentry of the Catalogue. So is theepicentral intensity, I₀, if providedby the original source. Following thesecriteria, a total of about 5,000earthquakes constitute the Catalogue.Although originally derived for the purposeof seismic hazard calculation within GSHAP,the Catalogue provides a data base for manytypes of seismicity and seismic hazardstudies.     

Regional Stress Field and Seismic Dynamics Along the Border Zone Between Fujian, Guangdong and Jiangxi Provinces

The regional stress field and seismic dynamics along the border zone between Fujian, Guangdong and Jiangxi Provinces are studied based on the seismo-geological data, GPS measurement, and seismicity. The results show that: (1) the principal compressional stress of the stress field is oriented in NW-SE direction and the principal extensional stress is in NE-SW direction; (2) the WNW-ward compression and collision of the Philippine Sea Plate to the eastern coast of Taiwan Island are the most direct and most important dynamic source for preparation and occurrence of strong earthquakes in the Taiwan area and along the border zone between Fujian, Guangdong and Jiangxi Provinces.     

大兴安岭阿龙山地区流纹岩风化的地球化学特征

通过大兴安岭地区两个流纹岩风化剖面的研究发现，大兴安岭地区的岩石风化过程具有特殊性。风化过程分为两个阶段，即以化学风化为主导的基质风化阶段和以机械风化为主导的斑晶风化阶段，第二阶段显示出与正常风化剖面相反的风化趋势。低温和长冬使第二风化阶段延长，并呈现逆风化趋势。风化过程中Fe和Al始终处于流失状态。上述特征的产生是由原岩的结构及成分、气候因素和生态系统等多种因素作用的结果。     

冲绳海槽南部沉积层序的粒度特征

对取自冲绳海槽南部的A2 3孔经前处理后的沉积物样品进行了粒度测试,探讨了陆源沉积层序的粒度特征。沉积物平均粒径、分选系数、偏态、峰态等粒度参数的变化显示出A2 3孔的沉积层序以 4 0 0cm为界可分为上、下两段,下段各参数稳定,代表了比较稳定的水动力条件的沉积环境;上段则波动较大,小规模浊流沉积频繁发育,暗示了不稳定的沉积环境。浊流层内粗粒与细粒组分含量及粒度分布的变化具有明显的规律性。通过分析A2 3孔陆源沉积层序的各沉积参数特征,认为冲绳海槽南部的沉积环境和动力在时间尺度上有较大的变化,东海陆架物质向南部海槽的输运可能是以峡谷为通道的重力作用引起的床底沉积作用为主。另外,对陆源碎屑和全样粒度结果的对比,显示了前处理方法对于海洋沉积物粒度分析的重要性.     

冠县引黄井渠结合灌区机井建设浅议

针对目前冠县引黄井渠结合灌区机井建设发展中主要存在机井发展不平衡、机井退化、老化、成井质量差等问题，因地制宜，提出了今后灌区发展机井建设的具体措施。     

山西五台县水泉湾泉和李家庄泉的成因分析

本文主要根据水泉湾泉和李家庄泉泉域的地质和水文地质资料，分析了本区内岩溶的发育特征和岩溶地下水的循环规律．研究分析了水泉湾泉和李家庄泉的形成原因。