轻便可控震源与夯击震源在金属矿地震勘探中的对比试验研究

可控震源具有分辨率高、频率范围选择自由、能量频谱有一定可控性等优点。但目前在浅层地质勘探中 ,尚缺乏可控、无损和高分辨率的震源。吉林大学国土资源部现代地球物理仪器开放研究实验室研制的轻便高频可控震源系统填补了国内这一空白。为验证其可靠性和稳定性 ,在河北省迁安大石河铁矿进行了轻便高频可控震源 (PHV )系统与夯击震源WACKERBS6 0Y系统的对比试验。试验结果表明 :高频可控震源工作稳定、效率高 ,较夯击震源有着较为明显的优点 ,且其地震反射剖面与夯击震源地震剖面具有良好的一致性。可控震源无疑将成为浅层工程、地质勘探无损探测的有力工具 ,具有广阔的应用前景。     

轻便可控震源在金属矿地震反射勘探的试验研究

在河北省迁安大石河铁矿进行轻便高频可控源 (PHV)地震反射勘探的试验研究是成功的。可控震源的优点主要在于分辨率高、可以自由选择频率范围 ,对输入到地下能量的频谱有一定的控制作用。通过与夯击震源WACKERBS60Y系统结果的对比 ,证实了它工作稳定 ,效率高 ,优于其它震源。     

适合于城市活断层探测中的激发震源

激发地震波的震源是地震勘探的关键因素,只有在震源激发出的地震波信号具有足够的能量和宽频带的前提下,才有可能接收到地下界面产生的反射波,也才使数据采集、处理和解释具有实际意义。这里介绍了二种用于城市活断层探测中的激发震源,并就其工作原理、技术指标、激发参数和对比试验效果进行了阐述,试验研究结果表明:夯击震源和可控震源均能满足城市活断层探测的需要。虽然如此,在城市活断层探测中,尤其在城市特定环境下(不允许炸药震源激发、各种外界干扰十分严重),仍需根据工作需要和测区实际情况,合理选取激发震源。     

戈壁地区不同震源激发效果的对比分析

以新疆哈密地区某煤田的三维地震勘探为例,选择同一区域、相同观测系统,分别采用炸药震源和可控震源激发,对其原始单炮记录和成果剖面进行了对比分析。结果发现:戈壁地区地震激发时炸药震源和可控震源在控制资料质量方面各有优势;原始单炮记录上,炸药震源原始单炮高频信号的频带较宽,而可控震源压制环境噪声效果更好;时间剖面上,可控震源的浅层反射波层次丰富、分辨率高于炸药震源,对尖灭点以及断层的显示更为清晰。      

电磁驱动可控震源在隧道探测中的应用

地震勘探对地下地质结构的调查是一种行之有效的方法。由于条件的限制,有些地区不适合采用炸药震源,而且炸药震源费用高、危险大。采用电磁驱动的高频可控震源,震源采用全新的电磁驱动方式,频率从10H z到1000H z,向地下发送可变频率振动。为验证高频可控震源野外工作的稳定性、可靠性、有效性,在鞍山东山隧道上进行了实际探测,与已知资料相比,得到了满意的结果。     

大吨位可控震源在西部巨厚砾石区地震勘探中的应用

在潜水位较深、巨厚砾石覆盖区,如何提高激发效果是煤田地震勘探面临的最大难题。通过对炸药震源及中小吨位、大吨位可控震源的对比,认为可控震源具有激发精确可控、效率高等优势;而大吨位可控震源又具有能量大、技术参数可控、震源一致性高等优点,尤其适合在中国西部地区巨厚砾石区的地震勘探。甘肃某勘探区震源的试验对比与煤田勘探效果说明,在反射品质较差的巨厚砾石区,只有使用大吨位可控震源,才能取得高品质的地震资料。     

利用可控震源进行高分辨率地震勘探

可控震源技术的发展，解决了困扰人们已久的激发地震信号频谱受谱受炸药量及激发介质诸因素制约的问题。     

可控震源参数选择及在煤田勘探中的应用

介绍了如何选择可控震源的扫描长度和震源台数、振动次数以及扫描频宽等参数，指出采用数台可控震源组合，增加扫描的总时间和利用相关技术是提高可控震源地震资料信噪比的有效方法，也是可控震源取得成功的关键。     

震源综述

70年代初期,随着地震勘探数字化和处理的计算机化,地震勘探所用的震源以及记录方式亦突破了传统的单一炸药震源和每炮得一张记录的格局。本文试图从震源原理的角度来讨论各种震源的类型,及其记录形式。     

也门71区山地激发技术

也门71区山地地质条件复杂,基岩裸露,激发条件差。提高山地资料品质,是改善地震资料品质的关键。分析旧地震资料,确定了山地激发技术的优化方向,进行了全面的激发参数试验,分别优选出可控震源和炸药震源激发因素,在开阔处采用可控震源激发,空炮段较大时用炸药震源补充。施工时首先详细踏勘,进行精细单线设计,采用弯线施工和变观等方法,多设可控震源激发点。采用优化的激发技术,地震资料品质得到明显提高。     

利用P波S波相结合的逆时偏移方法监测微地震群

微地震定位是油气资源开采中评估水力压裂质量和评估矿山地震和水库地震安全的重要手段。但是,采用地震震相 到时定位的方法很难对具有相近到时的微地震事件群精确定位地震。本文尝试用P波和S波结合的逆时偏移方法对具有相 近到时的微地震定位。先用绝对振幅记录做逆时偏移,获得P波和S波以及P波与S波结合的综合波场,再采用波前在震源 位置成像前后的汇聚到散射的转换过程作为成像条件,提取震源位置和发震时刻。用数值模拟生成具有相近到时的微地震 群,然后用该方法定位微地震。结果表明该方法可以有效提取各个震源位置和发震时刻。     

电磁式可控震源与大地耦合的研究

目前国内各大油田采用的可控震源 ,主要以车载液压式为主 ,频率低 ,重量大。耦合方式是把整车的重量压在激震器基板上 ,由于整车的重量远大于激振器的输出力 ,所以耦合效果较好。通过物理工程建模 ,研究了激震器所输出的力与底座、弹簧、配重的关系。使得实际工作中可以避免激震器与大地脱耦 ,实现在浅层地震勘探时将激震器产生的力最大限度的传入地下 ,并减少了系统的重量     

煤炭地下气化区高密度三维地震勘探技术研究

地下煤层气化的燃烧范围,气化燃烧热力影响边界、形态、方向,气化区冒落带的发展高度及气化煤层裂隙发育程度,是开展煤炭地下气化工程迫切需要解决的问题。基于煤炭地下气化工程试验区地震地质情况,从地震响应入手,在分析煤炭地下气化后地震波场响应特征的基础上,提出了运用高密度三维地震采集技术结合全三维地震属性解释技术,高精度识别煤炭地下气化燃烧范围、气化热力影响边界的方法。实际勘探成果表明,本方法地震成像清晰,预测精度高,与钻探结果吻合较好。     

人工震源地下介质变化动态监测

成像地球内部介质结构及其动态变化是地球物理学家的主要任务.相对于对地球介质静态结构的认识,对于地下介质性质随时间变化的了解明显不足.近年来随着观测资料的增加,已经开始利用重复地震和噪声等震源研究地下介质变化.受到源位置和时间等因素制约,基于地震和噪声等被动震源的观测结果的时间和空间分辨率有限.利用人工震源主动向地下发射...     

Seismic hazard in the Sannio-Matese area of Italy

The assessment of seismic hazard at five selected sites in the Sannio-Matese region is based on the computer program SRAMSC. Owing to the extensive historical data base for the output parameter, the MSK intensiy is chosen. The seismicity model is made up of five narrow area seismic sources. Circular or elliptical macroseismic fields are assigned to individual sources. A generalized Kövesligethy equation is used for this purpose as the attenuation relationship. The study reveals similar and a rather high hazard at the sites at Benevento, Boiano, and Melfi, which are located in the zone of highest seismic activity. At the Pomigliano and Lucera sites, the assessed hazard is much lower.     

Seismic Hazard Analysis — Quo vadis?

The paper is dedicated to the review of methods of seismic hazard analysis currently in use, analyzing the strengths and weaknesses of different approaches. The review is performed from the perspective of a user of the results of seismic hazard analysis for different applications such as the design of critical and general (non-critical) civil infrastructures, technical and financial risk analysis. A set of criteria is developed for and applied to an objective assessment of the capabilities of different analysis methods. It is demonstrated that traditional probabilistic seismic hazard analysis (PSHA) methods have significant deficiencies, thus limiting their practical applications. These deficiencies have their roots in the use of inadequate probabilistic models and insufficient understanding of modern concepts of risk analysis, as have been revealed in some recent large scale studies. These deficiencies result in the lack of ability of a correct treatment of dependencies between physical parameters and finally, in an incorrect treatment of uncertainties. As a consequence, results of PSHA studies have been found to be unrealistic in comparison with empirical information from the real world. The attempt to compensate these problems by a systematic use of expert elicitation has, so far, not resulted in any improvement of the situation. It is also shown that scenario-earthquakes developed by disaggregation from the results of a traditional PSHA may not be conservative with respect to energy conservation and should not be used for the design of critical infrastructures without validation. Because the assessment of technical as well as of financial risks associated with potential damages of earthquakes need a risk analysis, current method is based on a probabilistic approach with its unsolved deficiencies.

Traditional deterministic or scenario-based seismic hazard analysis methods provide a reliable and in general robust design basis for applications such as the design of critical infrastructures, especially with systematic sensitivity analyses based on validated phenomenological models. Deterministic seismic hazard analysis incorporates uncertainties in the safety factors. These factors are derived from experience as well as from expert judgment. Deterministic methods associated with high safety factors may lead to too conservative results, especially if applied for generally short-lived civil structures. Scenarios used in deterministic seismic hazard analysis have a clear physical basis. They are related to seismic sources discovered by geological, geomorphologic, geodetic and seismological investigations or derived from historical references. Scenario-based methods can be expanded for risk analysis applications with an extended data analysis providing the frequency of seismic events. Such an extension provides a better informed risk model that is suitable for risk-informed decision making.