An investigation of seismicity for the Central Anatolia region,Turkey

The aim of this study is to investigate the seismicity of Central Anatolia, within the area restricted to coordinates 30–35° longitude and 38–41° latitude, by determining the “a” and “b” parameters in a Gutenberg–Richter magnitude–frequency relationship using data from earthquakes of moment magnitude (Mw)?≥?4.0 that occurred between 1900 and 2010. Based on these parameters and a Poisson model, we aim to predict the probability of other earthquakes of different magnitudes and return periods (recurrence intervals). To achieve this, the study area is divided into six seismogenic zones, using spatial distributions of earthquakes greater than Mw?≥?4.0 with active faults. For each seismogenic zone, the a and b parameters in the Gutenberg–Richter magnitude–frequency relationship were calculated by the least squares method. The probability of occurrence and return periods of various magnitude earthquakes were calculated from these statistics using the Poisson method.     

Forward induced seismic hazard assessment: application to a synthetic seismicity catalogue from hydraulic stimulation modelling

The M _w 3.2-induced seismic event in 2006 due to fluid injection at the Basel geothermal site in Switzerland was the starting point for an ongoing discussion in Europe on the potential risk of hydraulic stimulation in general. In particular, further development of mitigation strategies of induced seismic events of economic concern became a hot topic in geosciences and geoengineering. Here, we present a workflow to assess the hazard of induced seismicity in terms of occurrence rate of induced seismic events. The workflow is called Forward Induced Seismic Hazard Assessment (FISHA) as it combines the results of forward hydromechanical-numerical models with methods of time-dependent probabilistic seismic hazard assessment. To exemplify FISHA, we use simulations of four different fluid injection types with various injection parameters, i.e. injection rate, duration and style of injection. The hydromechanical-numerical model applied in this study represents a geothermal reservoir with preexisting fractures where a routine of viscous fluid flow in porous media is implemented from which flow and pressure driven failures of rock matrix and preexisting fractures are simulated, and corresponding seismic moment magnitudes are computed. The resulting synthetic catalogues of induced seismicity, including event location, occurrence time and magnitude, are used to calibrate the magnitude completeness M _c and the parameters a and b of the frequency-magnitude relation. These are used to estimate the time-dependent occurrence rate of induced seismic events for each fluid injection scenario. In contrast to other mitigation strategies that rely on real-time data or already obtained catalogues, we can perform various synthetic experiments with the same initial conditions. Thus, the advantage of FISHA is that it can quantify hazard from numerical experiments and recommend a priori a stimulation type that lowers the occurrence rate of induced seismic events. The FISHA workflow is rather general and not limited to the hydromechanical-numerical model used in this study and can therefore be applied to other fluid injection models.     

On‐Site Vapor‐Phase Analysis as a Novel Approach for Monitoring Groundwater Wells

The results of comprehensive field testing of on‐site vapor‐phase‐based groundwater monitoring methods are presented to demonstrate their utility as a robust and cost‐effective approach for rapidly obtaining volatile organic compounds (VOCs) concentration data from a monitoring well. These methods—which rely on sensitive, commercially available field equipment to analyze vapor in equilibrium with groundwater—proved easy to implement and can be tailored to site‐specific needs, including multilevel sampling. During field testing, low‐flow groundwater concentrations could be reasonably estimated using submerged passive vapor diffusion samplers or field equilibration of collected groundwater (R² = 0.85 to 0.96). These two methods are not as reliant on in‐well mixing to overcome vertical stratification within wells as simpler headspace methods. The importance of well and aquifer‐specific factors on concentration data (and therefore method selection) is highlighted, including the effect of changing in‐well patterns due to seasonal temperature gradients. Results indicated that vertical stratification was relatively limited within the set of wells included in these studies, resulting in similar performance for short depth‐discrete passive vapor diffusion samplers (constructed from 40‐mL vials) and longer samplers (2.5 to 5 feet in length) designed to cover a larger portion of the screened interval. A year‐long, multi‐event evaluation demonstrated that vapor‐phase‐based monitoring methods are no more variable than conventional groundwater monitoring methods, with both types subject to similar spatial and temporal variability that can be difficult to reduce. Vapor sampling methods represent a promising approach for estimation of groundwater concentrations by reducing the cost liabilities associated with monitoring while providing a more sustainable approach.     

Persisting challenges for performance-based building assessment

Intense research and refinement of the tools used in performance-based seismic engineering have been made, but the maturity and accuracy of these methods have not been adequately confirmed with actual data from the field. The gap between the assumed characteristics of actual building systems and their idealized counterparts used for analysis is wide. When the randomly distributed flaws in buildings as they exist in urban areas and the extreme variability of ground motion patterns combine, the conventional procedures used for pushover or dynamic response history analyses seem to fall short of reconciling the differences between calculated and observed damage. For emergency planning and loss modeling purposes, such discrepancies are factors that must be borne in mind. Two relevant examples are provided herein. These examples demonstrate that consensus-based analytical guidelines also require well-idealized building models that do not lend themselves to reasonably manageable representations from field data. As a corollary, loss modeling techniques, e.g., used for insurance purposes, must undergo further development and improvement.     

Land cover mapping using time series HJ-1/CCD data

It is very difficult to have remote sensing data with both high spatial resolution and high temporal frequency; thus, two categories of land-use mapping methodology have been developed separately for coarser resolution and finer resolution data. The first category uses time series of data to retrieve the variation of land surface for classification, which are usually used for coarser resolution data with high temporal frequency. The second category uses fine spatial resolution data to classify different land surface. With the launch of Chinese satellite constellation HJ-1in 2008, four 30 m spatial resolution CCDs with about 360 km coverage for each one onboard two satellites made a revisit period of two days, which brought a new type of data with both high spatial resolution and high temporal frequency. Therefore, by taking the spatiotemporal advantage of HJ-1/CCD data we propose a new method for finer resolution land cover mapping using the time series HJ-1/CCD data, which can greatly improve the land cover mapping accuracy. In our two study areas, the very high resolution remote sensing data within Google Earth are used to validate the land cover mapping results, which shows a very high mapping accuracy of 95.76% and 83.78% and a high Kappa coefficient of 0.9423 and 0.8165 in the Dahuofang area of Liaoning Province and the Heiquan area of Gansu Province respectively.     

Diagenetic fluid evolution and water-rock interaction model of carbonate cements in sandstone: An example from the reservoir sandstone of the Fourth Member of the Xujiahe Formation of the Xiaoquan-Fenggu area,Sichuan Province,China

Carbonate cement is the most abundant cement type in the Fourth Member of the Xujiahe Formation in the Xiaoquan-Fenggu area of the West Sichuan Depression. Here we use a systematic analysis of carbonate cement petrology, mineralogy, carbon and oxygen isotope ratios and enclosure homogenization temperatures to study the precipitation mechanism, pore fluid evolution, and distribution of different types of carbonate cement in reservoir sand in the study area. Crystalline calcite has relatively heavy carbon and oxygen isotope ratios(δ13C = 2.14‰, δ18O = -5.77‰), and was precipitated early. It was precipitated directly from supersaturated alkaline fluid under normal temperature and pressure conditions. At the time of precipitation, the fluid oxygen isotope ratio was very light, mainly showing the characteristics of a mixed meteoric water-seawater fluid(δ18O = -3‰), which shows that the fluid during precipitation was influenced by both meteoric water and seawater. The calcite cement that fills in the secondary pores has relatively lighter carbon and oxygen isotope ratios(δ13C = -2.36‰, δ18O = -15.68‰). This cement was precipitated late, mainly during the Middle and Late Jurassic. An important material source for this carbonate cement was the feldspar corrosion process that involved organic matter. The Ca2+, Fe3+ and Mg2+ ions released by the clay mineral transformation process were also important source materials. Because of water-rock interactions during the burial process, the oxygen isotope ratio of the fluid significantly increased during precipitation, by about 3‰. The dolomite cements in calcarenaceous sandstone that was precipitated during the Middle Jurassic have heavier carbon and oxygen isotope ratios, which are similar to those of carbonate debris in the sandstone(δ13C = 1.93‰, δ18O = -6.11‰), demonstrating that the two are from the same source that had a heavier oxygen isotope ratio(δ18O of about 2.2‰). The differences in fluid oxygen isotope ratios during cement precipitation reflect the influences of different water-rock interaction systems or different water-rock interaction strengths. This is the main reason why the sandstone containing many rigid particles(lithic quartz sandstone) has a relatively negative carbon isotope ratio and why the precipitation fluid in calcarenaceous sandstone has a relatively heavier oxygen isotope ratio.     

Holocene slip rate and paleoearthquake records of the Salt Lake segment of the Northern Zhongtiaoshan Fault,Shanxi Province

The Northern Zhongtiaoshan Fault is a major deep fault at the southern margin of the Yuncheng Basin. There have been few studies on the fault, and the historical earthquakes are few and weak. However, the intensity of activity on the fault should never be underestimated. Through interpretations of aerial images, topography measurements and excavation of trenches, this paper studied the fault distribution, the surface deformation and the activity of the normal fault south of Salt Lake near the city of Yuncheng. By tracing faults in the three trenches, it was found that there had been at least three large paleoseismic events, at 1–3.5, 3.6–4.4 and 7.4–8.8 ka BP. Employing 14 C dating, we determined the same gravel layers in the uplifted side and downthrown side. Making differential Global Positioning System measurements of the vertical difference and topographic profile, we obtained the mean slip rate of the Northern Zhongtiaoshan Fault since 24.7 ka BP(0.75±0.05 mm/a). Using the results of relevant studies, we calculated the possible vertical fault displacement of one earthquake(2.35 m) and obtained the recurrence interval of characteristic earthquakes as 2940–3360 a after dividing the displacement by the mean slip rate.     

多维体视方法论及其在地球科学研究中的意义

本文阐述"多维体视方法论",主张立体透视与动态、多维地看问题;它起源于医学CT(计算机层析学)透视成像、核磁共振(MRI)等体视学方法研究疾病的生理解剖结构、病理特征、监测人体有关器官的各种变化,是行之有效的方法;已成功地应用于检测工业器械、航天器及地下结构等物体的内部结构,从而发展和演绎出来的认识论方法.在医学领域将CT 、MRI所得二维信息和断面图像、对病灶区引入"体显示"和"面显示"等可视化技术,将能充分反映不同疾病的病理、药理特征;在航天、地学等领域同样应用着CT多维"可视化技术".本文试图发扬综合预测的学术思想,将医学临床应用CT、核磁共振、体视学方法结合研究其他制约因素指标,从而区分出疾病的原发、继发分期,导致绝症的进程和前兆,概括为"多维体视预测方法";也适用于地震孕育、强震发生与火山喷发预测的研究.     

A study on the seismic behavior of a retrofitted building based on nonlinear static and dynamic analyses

This study describes the seismic performance of an existing five storey reinforced concrete building which represents the typical properties of low-rise non-ductile buildings in Turkey. The effectiveness of shear walls and the steel bracings in retrofitting the building was examined through nonlinear static and dynamic analyses. By using the nonlinear static analysis, retrofitted buildings seismic performances under lateral seismic load were compared with each other. Moreover, the performance points and response levels of the existing and retrofitting cases were determined by way of the capacity-spectrum method described in ATC-40 (1996). For the nonlinear dynamic analysis the records were selected torepresent wide ranges of duration and frequency content. Considering the change in the stiffness and the energy dissipation capacities, the performance of the existing and retrofitted buildings were evaluated in terms of story drifts and damage states. It was found that each earthquake record exhibited its own peculiarities, dictated by frequency content, duration, sequence of peaks and their amplitude. The seismic performance of retrofitted buildings resulted in lower displacements and higher energy dissipation capacity depending mainly on the properties of the ground motions and the retrofitting strategies. Moreover, severe structural damage (irreparable or collapse) was observed for the existing building. However, buildings with retrofit alternatives exhibited lower damage levels changing from no damage to irreparable damage states.