地质雷达探测技术在浅覆盖活动构造区填图中的应用——以宁夏青铜峡地区1:5万新构造与活动构造区填图为例

地质雷达探测以其分辨率高、定位准确、快速经济、灵活方便、剖面直观、实时图像显示等优点,成为地质调查中广泛使用的一种探测方法。本次宁夏青铜峡地区1∶5万新构造与活动构造区填图中运用地质雷达探测技术对第四系和隐伏断层进行了探测。结果表明,40 MHz地质雷达可以有效地探测地表以下30 m内的第四系结构,可清晰地识别出3套第四纪地层。这一地层结构划分被第四系浅钻证实,其为第四系全新统灵武组,自下而上由泥岩、砂砾石层和含砾的砂或泥等3套地层组成。对测区主干断裂——柳木高断裂南段的地质雷达探测表明,断裂带表现为近地表发散向下汇聚的正花状结构,这与探槽揭露的特征一致,表明地质雷达探测可以准确标定隐伏断层平面位置与垂向精细结构。本次宁夏地质填图证实,地质雷达技术是浅覆盖活动构造区进行隐伏断裂调查和第四纪地层层序划分的可行、高效、便捷的技术方法之一。

川滇活动构造区地震层析成像

应用一种新的地震体波层析成像方法确定川滇活动构造区(98°-105°E,22°-32°N)详细的三维P波速度结构.反演得到研究区0-85 km深度内几个截面上的P波速度图像.结果表明:(1)该地区地壳和上地幔的速度存在明显的横向不均匀性;(2)上地壳速度图像与地表地质特征明显相关,四川盆地呈现低速,高原地带为明显的高速区,沿康滇地轴为显著的高速条带;(3)10-85 km深度的速度图上腾冲火山附近形成一低速柱;(4)中地壳内存在一个大范围的低速层,这与区内人工地震测深所得到的结果基本吻合;(5)大型活动断裂带两侧存在明显的速度差异,而红河断裂带的影像在40 km的速度图上仍十分清楚,甚至到60 km深度还隐约可见,这也许说明红河断裂是切穿地壳的深大断裂;(6)强震位置与活动断裂及速度结构三者之间存在一定的关联性,大部分构造型强震发生在由大的活动断裂勾画的块体边界上,而那些发生在非大断裂附近的强震几乎都集中在下部中地壳存在低速带或由低速带向高速带过渡的位置.下部低速层的存在可能是上部中强地震活动的构造背景.

宁夏大坝站幅1:50 000地质图数据库

宁夏大坝站幅(J48E012016)1:50 000地质图是"宁夏1:50 000红崖子(J48E011016)、大坝站(J48E012016)、青铜峡铝厂(J48E013016)三幅新构造与活动构造区填图试点"子项目的区域地质调查工作之一,属于"特殊地质地貌区填图试点"计划项目。大坝站幅1:50 000地质图是依据《1:50 000区域地质调查技术要求》(DD2019-01)编制完成,在资料收集与数据准备、野外地质调查与填图成果过程中,均采用数字区域地质调查系统(DGSS)和MapGIS 6.7系统完成,有效实现了地质填图数值化。依据《数字地质图空间数据库建库标准》(DD 2006-06)等相关标准,在原始资料数据库基础上,建立了1:50 000地质图空间数据库。数据库有地质剖面(1:2 000)5条,钻孔6个,地质体156个,地质(界)线334条,产状340个,年代学样品41个,照片321个,素描图61个,河湖岸线与断层681个。数据容量约1.02 GB。本次地质图集中展示了测区新生代沉积、构造、地貌系统,填图工作探索了新构造-活动构造区地质填图思路、技术路线和成果表达方式,为特殊地质地貌区填图提供了参考。

Velocity Structure Beneath Active Faults and Seismic Tectonic Characteristics in the Beijing Area

Velocity structure beneath active faults in the Beijing area has been discussed,based on the digital crustal model of velocity from deep seismic sounding profiles and tomography imaging of P waves. We found that there exists nearly vertical deep faults beneath the Shunyi Depression and the Machiko Depression,which are very likely to be seismogenic faults in the future. In the superficial crust,the north segment of the Shunyi-QianmenLiangxiang fault,the north segment of the Huangzhuang-Gaoliying fault and the Qinghe fault show a trend to converge but without intersecting with vertical deep faults. This kind of seismo-tectonic state has great potential to generate large earthquakes.

Research on the Seismotectonic Zones and Seismicity State in the Southern Xinjiang Region

Based on the studies of earthquake activity, tectonic movement, crustal shortening rate, fault activity, local stress field and historical characteristics of strong earthquake activities in Xinjiang, we divide the south part of Xinjiang into 4 seismotectonic zones, namely, the eastern segment of south Tianshan seismic belt, the Kalpin block, the Kashi-Wuqia junction zone, and the west Kunlun Mountains seismic belt. Using earthquake catalogues from Xinjiang since 1900, and on the basis of integrity analysis of earthquake records in different magnitude ranges, the seismicity state of different seismotectonic zones is analyzed quantificationaUy by calculating the mean value of annual strain energy release, annual rate of earthquakes with different lower limits of magnitude, b-value, and the parameter m of accelerating strain release model. The characteristic indexes of seismicity state for each of the seismic tectonic zones are then determined, which provide a quantitative basis for earthquake tendency analysis and judgment.

Crustal Deformation Derived from GPS in the Chinese Mainland from 1991-2004

Based on GPS data from 1991- 2004 and the least-squares collocation method,we analyze the crustal deformation in the Chinese mainland. The results show that the first-order crustal deformation is unchanged in different periods in the Chinese mainland,which reflects the background of regional tectonic activity. The strain rate is much higher in Western China,especially in the Qinghai-Tibetan Plateau and Sichuan-Yunnan area. The variations in different periods are related with seismicity of strong earthquakes during the same time. The GPS data after 2004 shows the post-seismic deformation of the 2001 Kunlun Mountains M S8. 1 earthquake.

Relocation of Earthquakes in Shandong and Its Neighboring Areas,China and Its Relationship with Active Tectonics

Earthquakes taking place from 1975 to 2010 in and around Shandong Province are relocated using double-difference(HypoDD)and Hypoinvers 2000(Hypo2000)methods,after correction of the onset times of seismic phases.The results show that the relocated seismicity is clearly associated with regional tectonics in space,and is also in agreement with the existence of deep faults imaged by wide-angle and deep seismic reflection profiling;most of the focal depths are in the range of 5～25km,and there are clearly two predominant depths:10km and 16km,which are inferred to be on the bottom of the upper crust and in the middle crust,respectively.The pattern of seismic activity indicates that moderate and strong earthquakes are likely to occur in the brittle-ductile transition zone between the upper and the lower crust,as the outcome of the deep tectonic dynamic process and the movement and deformation of faults in the upper and shallow crust under the regional stress field.

Research on the Characteristics of the Coda Q Value in the Jiangsu Area

In this paper,research is conducted on the characteristics of coda Q values of the Jiangsu area,based on the Aki single backscattering model with the waveforms recorded by the Jiangsu digital seismic network. The results show that the Jiangsu area is a high Q value area as a whole,but the Q value differs obviously between different regions,characterized generally as high in the south and low in the north. This study focuses on 4 sub-regions where the stations are relatively dense,the tectonic features are distinguishing,and the calculation results of coda Q0 are fairly concentrated,and obtains the characteristic relationship between the Q value and frequency of the 4 regions. The region from south Jiangsu to the Yangtze River estuary and that around the Maoshan fault zone are the high Q value areas in Jiangsu; the region from central Jiangsu to the waterfront area is the low Q value area in Jiangsu Province,and the Lianyungang region in northern Jiangsu is the moderate Q value area. Comparing the tectonic activity and seismicity of the 4 different Q value sub-regions,there is a certain correlation between Q value,crustal movement and seismicity.

3-D geologic architecture of Xiong＇an New Area： Constraints from seismic reflection data

Studying the geologic architecture of the Xiong'an New Area will provide important basis for the evaluation of crustal stability, urban planning and infrastructural projects in this region, and it is also of great significance in exploring the occurrence of oil and gas, geothermal, hot dry rock and other resources. The stratigraphic system of the study area is established by using latest high quality seismic reflection and deep borehole data. Characteristics of the major faults developed in the study area are finely depicted with the method of structural analysis. Tectonic evolution of Xiong'an and adjacent areas is reconstructed by using balanced geological cross-section technique. The tectonic activity of the study area is discussed on the basis of the development of secondary faults and the distribution of active earthquakes across the region. This study demonstrates that Xiong'an New Area is located at the transfer zone of the central and northern Jizhong Depression. There are three regional unconformities developed in this area, by which four structural layers are sub-divided. Controlled by the Taihang Mountain piedmont fault, the Daxing fault, the Rongcheng fault and the Niudong fault, the structural framework of the study area is characterized by intervening highs with sags. This structural pattern has an important controlling over the reservoir characteristics, hydrocarbon accumulation and the distribution of geothermal resources and hot dry rock within this region. Rifting in this area began in the early Paleogene, exhibiting typical episodic character and became inactive in Neogene. The development feature of secondary faults along with the distribution of active earthquakes indicate that Xiong'an New Area has been in a relatively stable tectonic setting since the Neogene, while the Baxian Sag and other structural units to the east of it have obviously been in a rather active environment.