库木库里背斜活动性初步研究

库木库里盆地位于青藏高原北缘,与柴达木盆地一山之隔,是二者的过渡地带,也是高原主体部分向NE扩展的前缘地区;现今构造表现为被3条大型活动构造带(走滑的阿尔金断裂带、东昆仑断裂带和逆冲的祁漫塔格褶皱逆冲系)所夹持。因此,该盆地对于研究青藏高原北缘的构造活动性、活动历史,探讨高原的扩展模式具有十分重要的意义。虽然库木库里盆地南、北两侧均发育活动性很强的大型走滑断裂,但是在盆地中央发育1条大型背斜,走向NWW-SEE,与祁漫塔格褶皱逆冲系和柴达木盆地内的褶皱构造走向一致,说明盆地目前遭受NNE向的挤压。通过对盆地地形横、纵剖面和阶地展布形态的分析,得出背斜有自西向东扩展变形的特征;野外调查和测年结果显示,背斜东段冰川融水形成了大型冰水扇,形成年龄为(87.09±2.31)~(102.4±3.7)ka,进而获得背斜东段自晚更新世以来平均隆升速率的最大值为(2.78±0.28)~(3.28±0.28)mm/a。库木库里盆地整体的活动性很强,在构造上与其北边的柴达木盆地类似,都受控于阿尔金断裂南侧的NNE向的区域挤压作用。     

Landscape response to tectonic and climatic forcing in the foredeep of the southern Apennines,Italy: insights from Quaternary stratigraphy,quantitative geomorphic analysis,and denudation rate proxies

We present new data about the morphological and stratigraphic evolution and the rates of fluvial denudation of the Tavoliere di Puglia plain, a low‐relief landscape representing the northernmost sector of the Pliocene‐Pleistocene foredeep of the southern Apennines. The study area is located between the easternmost part of the southern Apennine chain and the Gargano promontory and it is characterized by several orders of terraced fluvial deposits, disconformably overlying lower Pleistocene marine clay and organized in a staircase geometry, which recorded the emersion and the long‐term incision history of this sector since mid‐Pleistocene times. We used the spatial and altimetric distribution of several orders of middle to late Pleistocene fluvial terraces in order to perform paleotopographic reconstruction and GIS‐aided eroded volumes estimates. Then, we estimated denudation rates on the basis of the terraces chronostratigraphy, supported by published OSL and AAR dating. Middle to upper Pleistocene denudation rates estimated by means of such an approach are slightly lower than 0.1 mm yr^‐1, in good agreement with short‐term data from direct and indirect evaluation of suspended sediment yield. The analysis of longitudinal river profiles using the stream power erosion model provided additional information on the incision rates of the studied area. Middle to late Quaternary uplift rates (about 0.15 mm yr^‐1), calculated on the basis of the elevation above sea level of marine deposits outcropping in the easternmost sector of the study area, are quite similar to the erosion rates average value, thus suggesting a steady‐state fluvial incision. The approach adopted in this work has demonstrated that erosion rates traditionally obtained by quantitative geomorphic analysis and k_sn estimations can be successfully integrated to quantify rates of tectonic or geomorphological processes of a landscape approaching steady‐state equilibrium. Copyright © 2014 John Wiley & Sons, Ltd.     

侧向侵蚀相关的走滑断裂滑动速率计算新方法

断层滑动速率是活动构造研究中的重要内容,是反映断裂活动性和地震危险性的重要参数之一。随着测年技术不断发展和测年精度大幅度提高,全新世甚至千年尺度和百年尺度的年轻地质体的位错也越来越多地被用于断层滑动速率计算。用走滑断裂带上地质体实测年龄计算滑动速率,会受到2种因素影响:1)累积位移时间是否与所测地质体年代相符合;2)地质体位移形成过程中会受到侵蚀。在利用全新世地质体计算断层滑动速率时,应将侧向侵蚀的影响剔除。因此,文中提出1种计算走滑断层滑动速率的新方法——差值法。走滑断层上河流阶地演化与断层位错分析表明,在阶地拔河高度存在较大差异的情况下,可以利用阶地拔河高度与年龄按比例进行计算。此方法在一定程度上提高了所计算滑动速率的精度,但是需要至少有3级不同阶地的拔河高度、年龄以及位错信息。若阶地拔河高度近似呈等差排列,即各级阶地上侧向侵蚀量近似相等的情况下,利用高-低阶地累积位错量之差与对应阶地年龄差来计算滑动速率,可以在一定程度上减少上述2种因素对滑动速率的影响。应用差值法计算得到阿尔金与昆仑断裂的滑动速率为4.7~8.8mm/a,与前人获得的地质学滑动速率、测地学滑动速率、缩短速率以及强震复发周期结果一致。     

Comparison of two extensometric stations in Hungary

Quartz-tube extensometers are used to measure rock deformations in two geodynamic observatories in Hungary in order to contribute to the investigation of recent tectonic movements on the area of the Pannonian Basin. One of the observatories is situated on the border of the Alps at Sopronbánfalva and is set in the metamorphic (gneiss) material of the mountains. The other station is in the basically karstic environment of the Mátyáshegy (Mátyás Hill) near Budapest. The aim of this paper is to investigate how the local conditions, such as structure of the observatory, topography or geologic features of the surrounding rocks, lead to additional or modified deformations of the extensometric stations. Data collected over eight years were processed and analysed to compare the observatories taking into account geologic, lithologic and topograpic properties of the measurement sites. Tidal and coherence analysis of the continuous strain measurements revealed that the instrument at Sopronbánfalva is more sensitive to atmospheric pressure loading than the extensometer at Mátyáshegy. Signal to noise values from the data processing of the short period variations support the higher stability of tidal strain measurements at Mátyáshegy. The strain rates measured by extensometers in both observatories are in good agreement with the strain rates inferred from GPS measurements of the Hungarian GPS Geodynamic Reference Network and the Central European GPS Reference Network.     

Two-dimensional physical-based inversion of confined and unconfined aquifers under unknown boundary conditions

An inverse method is developed to simultaneously estimate multiple hydraulic conductivities, source/sink strengths, and boundary conditions, for two-dimensional confined and unconfined aquifers under non-pumping or pumping conditions. The method incorporates noisy observed data (hydraulic heads, groundwater fluxes, or well rates) at measurement locations. With a set of hybrid formulations, given sufficient measurement data, the method yields well-posed systems of equations that can be solved efficiently via nonlinear optimization. The solution is stable when measurement errors are increased. The method is successfully tested on problems with regular and irregular geometries, different heterogeneity patterns and variances (maximum K_max/K_min tested is 10,000), and error magnitudes. Under non-pumping conditions, when error-free observed data are used, the estimated conductivities and recharge rates are accurate within 8% of the true values. When data contain increasing errors, the estimated parameters become less accurate, as expected. For problems where the underlying parameter variation is unknown, equivalent conductivities and average recharge rates can be estimated. Under pumping (and/or injection) conditions, a hybrid formulation is developed to address these local source/sink effects, while different types of boundary conditions can also exert significant influences on drawdowns. Local grid refinement near wells is not needed to obtain accurate results, thus inversion is successful with coarse inverse grids, leading to high computation efficiency. Furthermore, flux measurements are not needed for the inversion to succeed; data requirement of the method is thus not much different from that of interpreting classic well tests. Finally, inversion accuracy is not sensitive to the degree of nonlinearity of the flow equations. Performance of the inverse method for confined and unconfined aquifer problems is similar in terms of the accuracy of the estimated parameters, the recovered head fields, and the solver speed.     

高采样率四分量钻孔应变同震响应分析

In this paper, we adopt the observation data of two 10Hz YRY 4-component borehole strainmeters and one 100Hz FBS-3B broadband seismometer to study the responses of their observations to the April 11, 2012 Mw 8.6 earthquake off the west coast of northern Sumatra, and compare the response characteristics during the coseismic stage after preprocessing of the data. We analyze the spectrum＇s dynamic process during the coseismic stage with the S transformation method, and discuss the spectrum＇s details in different seismic phases. The S transformation results of the data of seismometer and borehole strainmeter at the same station show that the coseismic spectrum evolution of the two kinds of observation are similar to each other and can be cross-referenced in indentifying the wave signals, which proves that the borehole strainmeter measurements at high frequencies are reliable.     

四川前兆钻孔应变观测数据质量影响因素分析

钻孔应变观测的目的是为地震预测及地震科学研究提供高质量的观测数据,台站钻孔应变观测受到不同外界因素干扰时,观测数据的完整率和观测数据内精度也会不同程度地受到影响,对各种干扰因素的认识、分析、排除,是提高观测数据质量最好、也是最有效的途径。     

太阳能供电系统在天津测震台站的应用

利用太阳能供电系统解决天津市部分台站无法接入交流供电的问题,对部分台供电系统进行改造,采用复合式供电模式,避免农忙或雷雨季节停电问题,以提升台网整体数据传输连续率。     

Influence of confining pressure and impact loading on mechanical properties of amphibolite and sericite-quartz schist

In order to investigate the dynamic mechanical properties of amphibolite and sericite-quartz schist under confi ning pressure, two rocks are subjected to impact loadings with different strain rates and confi ning pressures by using split Hopkinson pressure bar equipment with a confi ning pressure device. Based on the experimental results, the stress-strain curves are analyzed and the effects of confi ning pressure and strain rates on the dynamic compressive strength, peak strain and failure mode are summarized. The results show that:(1) The characteristics of two rocks in the ascent stage of the stressstrain curve are basically the same, but in the descent stage, the rocks gradually show plastic deformation characteristics as the confi ning pressure increases.(2) The dynamic compressive strength and peak strain of two rocks increase as the strain rate increases and the confi ning pressure effects are obvious.(3) Due to the effect of confi ning pressure, the normal stress on the damage surface of the rock increases correspondingly, the bearing capacity of the crack friction exceeds the material cohesion and the slippage of the fractured rock is controlled, which all lead to the compression and shear failure mode of rock. The theoretical analysis and experimental methods to study the dynamic failure mode and other related characteristics of rock are useful in developing standards for engineering practice.