基于IPv6的地震观测网络模型探讨

地震台站的数据共享和安全访问是基于IPv4的地震观测网络系统急需解决的关键技术问题,由于IPv4的地址局限,缺乏安全认证和数据加密措施,现有的地震观测网络系统建立在私有IP地址的行业局域网,只能实现基于台网级的数据共享访问。下一代互联网IPv6协议取代IPv4是必然趋势,本研究以实现台站级数据访问为目标,构建在IPv6网络环境下地震观测网络系统的安全组网模型,同时针对现有观测系统的特点,探讨IPv4地震观测系统过渡到IPv6的系统模型,为下一步IPv6技术在地震行业的推广应用打下基础。     

江西省土地转移驱动力分析

This article explores the factors and mechanism driving the land-use conversion at regional level by developing and using an econometric approach which is called the simultaneous equations model (SEM). A case study in Jiangxi Province of China is conducted by establishing the SEM, which consists of three equations including agricultural production, land conversion of cultivated land to built-up area and land conversion of cultivated land to forest cover/grassland from 1988 to 2005. And then this paper employs the method of piecewise estimation to represent the influences of the factors such as population, society, economy, location and geophysical conditions on the process of land-use conversion in Jiangxi Province. Estimation results show that population is a predominant factor driving the land-use conversion at counties, while social and economic factors are determinant factors in the short term for the entire Jiangxi Province. Specifically, the size of agricultural population and the magnitude of agricultural input determine the agricultural production to a large extent; population size, plain area proportion at counties and land management policies together affect the direction and magnitude of conversion between cultivated land and built-up area; agricultural population proportion, terrain slope, grain production and non-agricultural industry promote the conversion of cultivated land to forest cover/grassland. Furthermore, the explored mechanism also reveals the underlying causes of the land use changes driven by a series of factors in Jiangxi Province. Finally, this paper concludes that factors proven to play an important role in driving the land-use conversion need to be considered when the land management agencies make out the land use planning to optimize the land use, expand the agricultural production, and conserve the cultivated land.     

地震计自噪声的研究

仪器的固有噪声水平是地震计的关键技术指标。 如何降低仪器的自噪声是地震计设计中需要解决的重要问题。 本文分析了产生地震计自噪声的两个主要噪声源: 布朗热噪声和电子噪声(1/f噪声), 以及它们对地震计传递函数的影响。 分析了三种地震计所记录的地震台台基噪声, 并且通过试验来检验仪器噪声对地震计观测数据的影响。     

Estimated Green's function extracted from superconducting gravimeters and seismometers

Estimated Green's function (EGF) between stations has been extracted from ambient seismic noise, direct surface wave and coda waves. It is also confirmed by laboratory experiments on ultrasonics and theoretical derivations assuming diffusive wave field, equi-partition of modes or random sources on an enclosed surface. This method provides a new approach to study the crust and mantle structure at regional scale, continental scale and global scale. Following the achievements with seismometer records, the records of infrasonic station, hydrophone and microphone were also used to obtain the EGFs of different wave fields. Since superconducting gravimeter is a better long period instrument than regular seismometer, EGF at longer period is expected to be obtained with the cross correlation of gravity data. In this paper, we will show the EGFs extracted by cross-correlations between the superconducting gravimeters and the seismometers. Both the travel times and dispersion curves obtained from different data types are consistent. The result shows that it is possible to retrieve the deep structure by the cross correlation of gravity data.     

GNSS参考框架点的选取对时序位移的影响

针对GNSS数据处理中框架点的选取, 以及GNSS数据处理与全球解绑定和相似变换参数的选取问题,设计4种计算方案,分析了各种尺度GNSS观测网下不同计算方案得到的时序位移差异。结果显示：对于各级GNSS网,在与全球H文件联合解算并满足相同相似变换要求的前提下,选择IGS05的全部框架点和从中较均匀地挑选部分框架点得到的结果差别并不显著。而对于大区域GNSS网,绑定全球解和不绑定全球解得到的结果有显著差别,ITRF2005下水平速度差别可达4 mm/a;对于中、小区域GNSS网,绑定全球解和不绑定全球解得到的整体相对运动差别不明显。     

Summary of Numerical Models for Predicting Productivity of Shale Gas Horizontal Wells

Shale gas production has gradually achieved high and stable output, which makes it possible to make up for the shortage of oil and gas energy as an alternative energy source. Shale reservoir is compact, with well-developed nano-pore, and has the characteristics of adsorption and desorption, diffusion and slippage. At the same time, there are a large number of natural cracks, bedding and foliation. Hydraulic fractures expand irregularly after volume fracturing in horizontal wells. The whole system has multi-field coupling and cross-scale flow effects. Productivity prediction of shale gas is difficult and uncertain, which restricts the efficient development and evaluation of shale reservoirs. In this paper, the development status of productivity numerical models for shale gas horizontal wells is reviewed in consideration of the multi-scale transport characteristics of shale gas. These models include dual media capacity models, multiple media capacity models, and complex seam productivity models. It is considered that the dual medium and multi-media productivity models weaken the large permeable flow area and channel provided by the complex seam network system after shale reservoir lamination, and cannot comprehensively characterize the full-scale coupled transport characteristics of shale gas. The numerical model for productivity prediction of shale gas horizontal wells based on complex fracture network provides a multi-scale flow embedded fracture network system, which solves the problem of systematic flow without losing the ability to accurately characterize each scale flow. It is necessary to obtain the complex fracture network morphological characterization which conforms to reservoir geological characteristics, rock mechanical behavior and fluid-solid coupling mechanism. Fracture network characterization is the key to the productivity prediction of shale gas horizontal wells.     

尼泊尔西部代莱克(Dailekh)地区石油地质条件分析

分析尼泊尔石油地质条件对于促进尼泊尔油气的勘探开发有重要意义。本文通过全面搜集尼泊尔油气地质及相关资料,结合实地考察和部分样品分析结果,报道了尼泊尔区域地质特征、油气勘探现状、区域构造特征和地层发育特征;分析了Dailekh地区出露的油气苗特征、烃源条件、生储盖和油气圈闭条件,认为Dailekh地区发育四套烃源岩层,多个生储盖组合,具有较好的油气勘探前景;油气苗为高成熟烃源岩裂解的产物,可能来自变质岩推覆体下伏沉积岩层;断层和逆冲相关的背斜、突起构造和倾斜断块等是找油气的重要构造。     

吉林松原M≥5.0震群前地磁谐波振幅比异常特征

以东北地区(40°—50°N,120°—130°E)为研究区域,利用黑龙江、吉林和辽宁地区地磁观测数据,进行谐波振幅比计算,对2013年10月31日至11月23日吉林松原接连发生的5个M≥5.0震群前该研究区地下电性结构进行分析,发现:(1)在该区域内显著地震发生前,望奎、通河、三岗、通化和铁岭地震台均出现下降—转折—恢复的异常变化特征,持续时间1—4.5年,变化幅度为0.04—0.07,而通河台Y_(ZH_y)项的不同周期间存在不同步现象,且异常持续2年以上;(2)通河台分钟值谐波振幅比具有由深至浅的周期迁移特征,三岗台秒值数据结果 Y_(ZH_y)向具有由浅入深的迁移特征;(3)2014年3月至2016年4月通河台水平方向的EW向数据不同深度介质电性出现差异性异常,可能预示着该台周边具有发生中强地震的危险,应重点关注该异常变化。     

江苏省数字强震动台网运行与维护

介绍江苏省数字强震动台网布局、强震动仪器观测环境及技术系统组成,并阐述强震动台网运行以及运行设备存在的常见故障和解决措施。江苏省数字强震动台网布局合理、性能稳定、动态范围大,地震记录信息完整可靠,丰富并充实了江苏省强震动数据库,为工程结构的抗震设计及地震工程学研究提供了宝贵的基础数据。     

Application of Machine Learning Methods in Arrival Time Picking of P Waves from Reservoir Earthquakes

Reservoir earthquake characteristics such as small magnitude and large quantity may result in low monitoring efficiency when using traditional methods. However, methods based on deep learning can discriminate the seismic phases of small earthquakes in a reservoir and ensure rapid processing of arrival time picking. The present study establishes a deep learning network model combining a convolutional neural network (CNN) and recurrent neural network (RNN). The neural network training uses the waveforms of 60 000 small earthquakes within a magnitude range of 0.8-1.2 recorded by 73 stations near the Dagangshan Reservoir in Sichuan Province as well as the data of the manually picked P-wave arrival time. The neural network automatically picks the P-wave arrival time, providing a strong constraint for small earthquake positioning. The model is shown to achieve an accuracy rate of 90.7% in picking P waves of microseisms in the reservoir area, with a recall rate reaching 92.6% and an error rate lower than 2%. The results indicate that the relevant network structure has high accuracy for picking the P-wave arrival times of small earthquakes, thus providing new technical measures for subsequent microseismic monitoring in the reservoir area.