Early Analogue Modeling Experiments and Related Studies to Today's Problems of Geo-electromagnetic Exploration

As I learned it from extensive geo-electromaguetic analogue modeling experiments, some specific nonconventional interpretation parameters, in certain conditions, give more detailed information about the geometry of subsurface resistivity inbomogeneities than the routinely used parameters. In this article, I show several examples, and I present how these early results influenced our later research. An enhanced geometric sensitivity may be due to special array geometry (as we call It "null array"), or it may be due to a narrow and very special frequency range (Le., the so-called "keyhole" range). Nonconventional but physically based interpretation parameters (like the Poyuting vector) or higher order invariants of resistivity or impedance tensors may also give useful additional information about the shape of subsurface bodies. One should be very careful in their application because a large part of these nontroditioual approaches are strongly constrained by measuring errors and geological noise.     

西藏高原上地幔的精细结构与构造--地震层析成像给出的启示

用布置在亚东—格尔木的164个流动地震台站记录的926个远震事件的24241条射线,进行远震P波层析成像处理,高分辨率的西藏高原上地幔的速度结构图,显示了印度巨厚地幔岩石圈在向高原之下推进的过程中,在高喜马拉雅之下拆分成上、下两层,这是发生的第一次拆沉. 下层从高喜马拉雅以下约以22°的角度向高原北部插入到350km 深;而其上层则向北伸展直到雁石坪,并构成了高原薄的地幔岩石圈. 在雁石坪北（33.7°N）,当其与亚洲大陆岩石圈地幔相遇后发生断离并下沉. 再次证实了五道梁（35.27°N）深部低速体的存在,本区内地壳内低速物质可能与上述运动有联系,反映了深层热物质的上涌.     

Episodic orogeny deduced from coeval sedimentary sequences in the foreland basin and its implication for uplift process of Longmen Mountain, China

Longmen Mountain located at the boundary between the Sichuan Basin and Tibetan Plateau,representing the steepest gradient of any edges of the plateau.Three endmember models of uplift process and mechanism have been proposed,including crustal thickening,crustal flow,and crustal isostatic rebound.Here we use coeval sedimentary sequences in the foreland basin to restraint uplift process and mechanism in the Longmen Mountain.The more than 10,000 m thick Late TriassicQuaternary strata filled in this foreland basin and can be divided into six megasequences that are distinguished as two distinct types.The first type is the wedge-shaped megasequences which are sedimentary response of strong active thrust loading events,characterized by a high rate of subsidence and sediment accumulation,coarsening-upward succession and a dual-sourced sediment supply.This type includes Late Triassic,Late Jurassic to Early Cretaceous and Late Cretaceous to Paleogene megasequences.The second type is the tabular megasequences,characterized by the low rate of subsidence and sediment accumulation,finingupward succession,and a single-sourced sediment supply,which is sedimentary response of isostatic rebound and erosion unloading.This type includes the Early to Middle Jurassic,Middle Cretaceous and Neogene to Quaternary megasequences.Basing on sedimentary,active tectonic,geomorphic evidence,we infer that the direction has been reversed from SSWdirected sinistral strike-slip to NNE-directed dextral strike-slip during 40-3.6 Ma,and since 3.6 Ma,the Longmen Mountain thrust belt belong to times of isostatic rebound and erosional unloading with NNEdirected dextral strike-slip.This suggests that crustal isostatic rebound is a primary driver for uplift and topography of the present Longmen Mountain.The Wenchuan(Ms8.0) earthquake,which ruptured a large thrust fault with NNE-directed dextral strikeslip along the range front,is an active manifestation of this crustal isostatic rebound process with dextral strike-slipping and shortening.This process may be the cause for the Wenchuan Earthquake and the apparent paradox of high relief,little shortening,the relative dearth of historical seismicity in the region.     

Field test of the superconducting gravimeter as a hydrologic sensor

We report on a field test of a transportable version of a superconducting gravimeter (SG) intended for groundwater storage monitoring. The test was conducted over a 6-month period at a site adjacent to a well in the recharge zone of the karstic Edwards Aquifer, a major groundwater resource in central Texas. The purpose of the study was to assess requirements for unattended operation of the SG in a field setting and to obtain a gravimetric estimate of aquifer specific yield. The experiment confirmed successful operation of the SG, but water level changes were small (<0.3 m) leading to uncertainty in the estimate of specific yield. Barometric pressure changes were the dominant cause of both water level variations and non-tidal gravity changes. The specific yield estimate (0.26) is larger than most published values and dependent mainly on low frequency variations in residual gravity and water level time series.     

Assessment of the effects of a marine urban outfall discharge on caged mussels using chemical and biomarker analysis

To assess the presence of endocrine disruptors in treated marine outfall discharges and their possible effects, mussels (Mytilus galloprovincialis) were caged in the environmental mixing zone of the outfall of the Santander sanitation system and in one control area. After 30, 60 and 90 days, samples were collected to perform chemical analyses (metals, anionic surfactants, alkylphenols, bisphenol A, phthalates and estrogenic hormones), biomarkers of general stress (lysosomal membrane stability-LMS, histopathology) and biomarkers of endocrine disruption (vitellogenin-like proteins and gonad index). There were no significant differences between outfall and control sites on contaminant levels, except for 4-tert-octylphenol which was higher in the outfall site. Bacteriological counts were higher in the outfall area. No relevant differences in biomarkers were detected between treated and control mussels. A significant reduction in LMS occurred in both groups after 90 days caging, indicating a stress situation possibly related to caging or to post-spawning reproductive state.     

A high-resolution real-time forecasting system for predicting the fate of oil spills in the Strait of Bonifacio (western Mediterranean Sea)

The Strait of Bonifacio is a long and narrow area between Corsica and Sardinia. To manage environmental emergencies related to the spill of oil from vessels, an innovative forecasting system was developed. This tool is capable of operationally predicting the dispersion of hydrocarbon spills in the coastal area of the Bonifacio Strait, either from an instantaneous or continuous spill and either in forward or backward mode. Experimental datasets, including ADCP water current measurements and the trajectories of drifter buoys released in the area, were used to evaluate the accuracy of this system. A comparison between the simulation results and experimental data revealed that both the water circulation and the surface transport processes are accurately reproduced by the model. The overall accuracy of the system in reproducing the transport of an oil spill at sea was estimated for both forward and backward prediction mode and in relation to different forecasting time lags.     

Island shadow effects and the wave climate of the Western Tuamotu Archipelago (French Polynesia) inferred from altimetry and numerical model data

To implement a numerical model of atoll lagoon circulation, we characterized first the significant wave height (Hs) regime of the Western Tuamotu Archipelago and the local attenuation due to the protection offered by large atolls in the south Tuamotu. Altimetry satellite data and a WAVEWATCH III two-way nested wave model at 5km resolution from 2000 to 2010 were used. Correlation between altimetry and model was high (0.88) over the period. According to the wave model, the archipelago inner seas experienced attenuated Hs year-long with a yearly average Hs around 1.3m vs a minimum of 1.6m elsewhere. The island shadow effect is especially significant in the austral winter. In contrast with southern atolls, Western Tuamotu experienced only few days per year of Hs larger than 2.5m generated by very high Hs southern swell, transient western local storms, strong easterly winds, and during the passage of distant hurricanes.     

阿留申岛弧的非火山颤动

在阿留申岛弧观测到了一些非火山颤动。在数座火山上的大跨区的地震台网也监测到颤动状的事件,因此不可能与任何一座火山体有关。虽然目前还不能给这些颤动定位,但我们根据多个台网的反射时差和振幅给出了大概的位置。多数非火山颤动是在所推断的太平洋消减板块闭锁区或从蠕动到闭锁转换区记录到的。有一次非火山颤动事件是在拉特群岛和安德烈亚诺夫群岛附近地区地震活动和火山活动增强时期记录到的。类似的同步增加以往在阿留申群岛记录到过,并被假设是由慢滑动事件引起的大范围应力变化造成的。2008年7月12日奥克莫克火山喷发约1小时后在科罗文和大锡特金地震台网记录到显著的非火山颤动。非火山颤动并不是分散地出现在整个阿留申岛弧,而似乎是集中在几个地区。用2500km的消减带,我们有机会检查这些地区并将其与不产生非火山颤动地区加以比较,以便确定产生该颤动的作用因素。     

滑坡编目:地震滑坡危险性分析中必不可少的部分

详细精确的滑坡编目是地震滑坡危险性分析工作中必不可少的一部分。理想的编目要满足如下条件:覆盖整个地震影响区;应包含所有可调查到的滑坡,滑坡的最小长度应小至1～5m左右;编目中的滑坡位置也必须准确,应使用能够反应它们真实的平面形状的区要素来表征。符合上述要求的滑坡编目可以用来进行地震滑坡危险性分析和其他的定量分析研究。详细的地震滑坡编目可以追溯到1960年代初的航空摄影技术的出现与应用。近年来,随着空间技术科学的进步,高分辨率卫星影像获取成为可能,从而使得除最小的滑坡之外可以识别并绘出所有由地震事件触发的滑坡。得益于遥感技术的这种可以观测到地球任何地方的能力,我们可以获取到任何大量地震滑坡发生区域的遥感影像。然而,随着高分辨率遥感影像时代的到来,地震滑坡编目数据不完整也成为当前研究中的一个普遍存在的问题。     

Temporal and Spatial Distribution of the Late Devonian (Famennian) Strata in the Northwestern Border of the Junggar Basin, Xinjiang, Northwestern China

The base of the Saerba Member (Mbr) of the Hongguleleng Formation (Fm.) probably lies in the Famennian Palmatolepis crepida Zone; the Longkou Mbr is probably a sedimentary wedge that thins out northwards; the Duguer Mbr has an approximate age from the upper part of the Pa. marginifera Zone or the Lower Pa. rugosa trachytera Zone through the top of the Pa. perlobata postera Zone; the Wulan Mbr has an age approximately corresponding to the whole Pa. gracilis expansa Zone. In the Bulongguoer section, the Lower Mbr of the Hongguleleng Fm. corresponds to Famennian Pa. crepida Zone through Pa. marginifera Zone; the Middle Mbr probably ranges from the Pa. r. trachytera Zone through the Pa. g. expansa Zone. The basal Namu Mbr of the Heishantou Fm. is probably the product during and after the Hangenberg Event in the upper part of the Siphonodella praesulcata Zone, which is still within the Devonian. In this context, the underlying Chasi Mbr may approximately correspond to the lower part of the S. praesulcata Zone (before the Hangenberg Event). Lateral distribution of strata indicates that the Upper Devonian in the Gennaren and Saerba areas each constitutes a structure of syncline, which differs from the previous recognition of a monocline structure.