基于Matlab的断裂带温泉水地球化学特征及地震活动性研究

基于Matlab开发出地下流体分析软件,对比分析了甘肃西秦岭北缘的武山、街子和清水温泉水化学组分特征;初步分析了温泉水水质类型、补给来源、水-岩平衡状态以及循环深度,并讨论了温泉水深循环对地震活动性的影响.研究表明温泉水均为大气降水成因,其水化特征受围岩的控制作用;清水温泉水的成熟度没有武山和街子温泉水高.地下水循环深度较浅的武山温泉和街子温泉水化类型属于Na-HCO3·SO4·Cl,所处断裂的地震活动频繁;地下水循环深度较深的清水温泉水化类型属于Na-SO4·Cl,所处断裂的地震活动性弱.     

禾青井动水位对断层蠕动与慢地震过程的响应初析

以湖南禾青井深井水位观测的异常图象为例进行定性分析，发现动水位观测有可能直接反映出断层的滑动或断层的慢地震过程，前者可能为地下水物理参量的观测与研究提供亲折思路，后者则可能对震源物理学的发展和地震预报水平的提高具有特殊的意义。     

Frictional heat generation and seismic radiation in a foam rubber model of earthquakes

Results from a study of stick-slip particle motion at the interface between two stressed foam rubber blocks indicate that normal vibrations and interface separation are an important part of the stick-slip process in foam rubber. The dimension of the dynamic slip pulse is small compared to the dimension of the model (approximately 10 cm vs. 200 cm) consistent with the abrupt-locking slip pulse model ofBrune (1970, 1976), andHeaton (1990). A comparison of frictional heat generation between stable-sliding and stick-slip foam rubber models indicates a linear relation between the temperature increase on the fault surface (for a given distance of slip) and the driving shear force for the stable-sliding model, while for the stick-slip model there is essentially no variation in frictional heat generation with an increase in shear stress. We performed experiments to investigate the ratio of normal motion to shear motion at different levels of normal stress in the stick-slip foam rubber model. Preliminary result indicate that the normal component of the particle motion increases more rapidly with increasing normal stress than the shear component. The phenomenon of interface separation and normal vibrations may thus explain some of the most frustrating problems in earthquake mechanics, e.g., the heat flow paradox, the long-term weakness of major active faults, and anomalousP-wave radiation.     

Imaging the ramp–décollement geometry of the Chelungpu fault using coseismic GPS displacements from the 1999 Chi-Chi, Taiwan earthquake

We use coseismic GPS data from the 1999 Chi-Chi, Taiwan earthquake to estimate the subsurface shape of the Chelungpu fault that ruptured during the earthquake. Studies prior to the earthquake suggest a ramp–décollement geometry for the Chelungpu fault, yet many finite source inversions using GPS and seismic data assume slip occurred on the down-dip extension of the Chelungpu ramp, rather than on a sub-horizontal décollement. We test whether slip occurred on the décollement or the down-dip extension of the ramp using well-established methods of inverting GPS data for geometry and slip on faults represented as elastic dislocations. We find that a significant portion of the coseismic slip did indeed occur on a sub-horizontal décollement located at 8 km depth. The slip on the décollement contributes 21% of the total modeled moment release. We estimate the fault geometry assuming several different models for the distribution of elastic properties in the earth: homogeneous, layered, and layered with lateral material contrast across the fault. It is shown, however, that heterogeneity has little influence on our estimated fault geometry. We also investigate several competing interpretations of deformation within the E/W trending rupture zone at the northern end of the 1999 ground ruptures. We demonstrate that the GPS data require a 22- to 35-km-long lateral ramp at the northern end, contradicting other investigations that propose deformation is concentrated within 10 km of the Chelungpu fault. Lastly, we propose a simple tectonic model for the development of the lateral ramp.     

郯庐断裂带的断裂活动对渤海东部中、新生代裂谷盆地发育的控制作用

郯庐断裂带自南而北穿越渤海东部,自中生代中期至新生代中期表现裂谷发育特征。裂谷发育经历两个旋回,各旋回的裂谷发育演化、盆地分布格局,沉积相带,沉积补偿速度等均受断裂带的断裂活动的强烈控制。     

The presence, characteristics and earthquake implications of the St. Lawrence fault zone within and near Lake Ontario (Canada–USA)

Questions persist concerning the earthquake potential of the populous and industrial Lake Ontario (Canada–USA) area. Pertinent to those questions is whether the major fault zone that extends along the St. Lawrence River valley, herein named the St. Lawrence fault zone, continues upstream along the St. Lawrence River valley at least as far as Lake Ontario or terminates near Cornwall (Ontario, Canada)–Massena (NY, USA). New geological studies uncovered paleotectonic bedrock faults that are parallel to, and lie within, the projection of that northeast-oriented fault zone between Cornwall and northeastern Lake Ontario, suggesting that the fault zone continues into Lake Ontario. The aforementioned bedrock faults range from meters to tens of kilometers in length and display kinematically incompatible displacements, implying that the fault zone was periodically reactivated in the study area. Beneath Lake Ontario the Hamilton–Presqu'ile fault lines up with the St. Lawrence fault zone and projects to the southwest where it coincides with the Dundas Valley (Ontario, Canada). The Dundas Valley extends landward from beneath the western end of the lake and is marked by a vertical stratigraphic displacement across its width. The alignment of the Hamilton–Presqu'ile fault with the St. Lawrence fault zone strongly suggests that the latter crosses the entire length of Lake Ontario and continues along the Dundas Valley.The Rochester Basin, an east–northeast-trending linear trough in the southeastern corner of Lake Ontario, lies along the southern part of the St. Lawrence fault zone. Submarine dives in May 1997 revealed inclined layers of glaciolacustrine clay along two different scarps within the basin. The inclined layers strike parallel to the long dimension of the basin, and dip about 20° to the north–northwest suggesting that they are the result of rigid-body rotation consequent upon post-glacial faulting. Those post-glacial faults are growth faults as demonstrated by the consistently greater thickness, unit-by-unit, of unconsolidated sediments on the downthrown (northwest) side of the faults relative to their counterparts on the upthrown (southeast) side. Underneath the western part of Lake Ontario is a monoclinal warp that displaces the glacial and post-glacial sediments, and the underlying bedrock–sediment interface. Because of the post-glacial growth faults and the monoclinal warp the St. Lawrence fault zone is inferred to be tectonically active beneath Lake Ontario. Furthermore, within the lake it crosses at least five major faults and fault zones and coexists with other neotectonic structures. Those attributes, combined with the large earthquakes associated with the St. Lawrence fault zone well to the northeast of Lake Ontario, suggest that the seismic risk in the area surrounding and including Lake Ontario is likely much greater than previously believed.     

南海东北部新构造运动及其动力学机制

南海东北部地处欧亚板块与菲律宾海板块的交汇区,新构造运动活跃。根据地震活动性、震源机制解和GPS资料对该区的新构造活动特征进行分析,在此基础上讨论该区新构造运动的动力学机制。分析发现,菲律宾海板块NW向俯冲对该区的影响最为显著,导致了该区较强的地震活动性以及与俯冲方向一致的构造应力场。而印藏碰撞产生的侧向应力传递也影响到该区,控制华南地块向SE方向运动,并与菲律宾海板块的NW向俯冲共同作用,使华南地块在SE向运动的同时伴有逆时针旋转。印藏碰撞的SE向应力传递对俯冲产生的NW向水平挤压的抵消作用,使得地震活动性自东向西减弱以及构造应力场P轴方位角顺时针旋转。在这一背景下,区内滨海断裂带的活动控制了该区的地震、海岸带构造升降等新构造运动。     

Position and velocity reliability testing in degraded GPS signal environments

Reliability testing, namely receiver autonomous integrity monitoring (RAIM), consists of statistical testing of least-squares residuals of observations, e.g., on an epoch-by-epoch basis aiming towards reliable navigation fault detection and exclusion (FDE). In this paper, classic RAIM and FDE methods are extended with testing of range-rate residuals to find inconsistent velocity solutions in order to contribute to the reliability of the system with special focus on degraded signal environments. Reliability enhancement efforts discussed include a Backward-FDE scheme based on statistical outlier detection and an iteratively reweighted robust estimation technique, a modified Danish method. In addition, measurement weighting assigned to code and Doppler observations is assessed in the paper in order to allow fitting a priori variance models to the estimation processes. The schemes discussed are also suitable in terms of computational convenience for a combined GPS/Galileo system. The objective of this paper is to assess position and velocity reliability testing and enhancement in urban and indoor conditions and to analyze the navigation accuracy conditions with high sensitivity GPS (HSGPS) tests. The results show the necessity of weighted estimation and FDE for reliability enhancement in degraded signal-environment navigation.     

PRELIMINARY STUDY OF PALEOEARTHQUAKES ON THE MIDDLE-EASTERN SEGMENT OF JINTA NANSHAN FAULT

Hexi Corridor is located at the northeastern margin of the Tibetan plateau. Series of late Quaternary active faults are developed in this area. Numerous strong earthquakes occurred in history and nowadays. Jinta Nanshan fault is one of the boundary faults between the Qinghai-Tibet block and the Alxa block. The fault starts from the northwest of Wutongdun in the west, passes through Changshan, Yuanyangchi reservoir, Dakouzi, and ends in the east of Hongdun. Because the Jinta Nanshan fault is a new active fault in this region, it is important to ascertain its paleoearthquakes since late Pleistocene for the earthquake risk study. Previous studies were carried out on the western part, such as field geomorphic investigation and trench excavation, which shows strong activity in Holocene on the western segment of Jinta Nanshan fault. On the basis of the above research, in this paper, we carried out satellite image interpretation, detailed investigation of faulted landforms and differential GPS survey for the whole fault. Focusing on the middle-eastern part, we studied paleoearthquakes through trench exploration on the Holocene alluvial fan and optical luminescence dating. The main results are as follows:Early Pleistocene to late Pleistocene alluvial strata are widely developed along the fault and Holocene sediment is only about tens of centimeters thick. The Jinta Nanshan fault shows long-lasting activity since late Quaternary and reveals tens of centimeters of the lowest scarp which illustrates new strong activity on the middle-east segment of this fault. Since late Pleistocene, 4 paleoearthquakes happened respectively before(15.16±1.29) ka, before(9.9±0.5) ka, about 6ka and after(3.5±0.4) ka, revealed by 4 trenches, of which 2 are laid on relatively thicker Holocene alluvial fan. Two events occurred since middle Holocene, and both ruptured the whole fault.     

抽水作用下先期断裂对地裂缝的影响研究

过度抽取地下水和先期存在的断裂构造是西安市地裂缝地质灾害发生的主要原因。作者首先从理论上分析了抽水情况下地裂缝形成的张拉破裂机制、剪切破裂机制和张剪复合破裂机制,并从结构面控制理论分析了先期断裂在地裂缝形成中的控制作用;然后依据比奥三维固结理论,采用FLAC软件建立了西安地裂缝的计算模型,比较了抽水作用时没有先期断裂和地层差异、有先期断裂而没有地层差异、有地层差异而无先期断裂等情况时的地面变形特征,得出抽水作用下,先期断裂对地裂缝的形成及发展具有诱导、隔离和放大的耦合作用,从而得出先期断裂不仅仅只是地裂缝形成的构造基础的结论。