正(2016年11月21日)这次会议是中国地质矿产经济学会召开的一次全国地勘行业的重要会议。张少农理事长亲自指导会议的筹备,因有重要工作不能参会,专门向姜大明部长做了报告。姜部长高度重视,委托我来参加会议。借这个机会,我代表部党组、代表姜大明部长,代表张少农理事长,向大家并通过大家向地勘行业广大干部职工表示诚挚的问候!

2006年6月在武汉召开了第二届环境与工程地球物理国际会议．会议围绕近年来兴起的近地表探测问题展开，涉及方法原理、仪器采集、资料处理等各个环节，反映出国内外环境与工程探测领域的若干前沿热点和发展动态．结合本次会议，可以看出该学科主要趋势为：应用领域不断扩宽，方法技术灵活多样，重视基础理论研究，开发新型（特种）仪器，通过高精度测量、延时测量、先进的数据处理技术和信息技术等手段改善探测质量．我国对环境与工程地球物理有很大的需要，应根据我国实际情况，吸收国外先进经验，积极开展自主创新．

近年来,城市工程地球物理探测技术得到了较快发展,并取得良好应用效果。城市工程地球物理探测具有很多特点,地面探测方法、地球物理测试方法、水声探测方法以及井中探测方法等各有所长,可以为岩土工程、地质灾害防治和环境问题研究提供有益的信息和数据,在实际应用中具有明显的技术优势。在实际中应该注重应用条件适应性、开展方法试验和综合物探。结合实际加强技术方法、仪器设备等方面的研究,将会推进城市工程地球物理探测技术得到更广泛应用与发展。

Two examples of multicomponent shear (S)-wave, shallow, seismic reflection profiling from urban en-vironments in eastern Canada are presented to examine the benefits of shear-wave reflection data and the latest developments in acquisition methodology, as well as our evolving understanding of the complex nature of seismic-wave propagation. In "soft" soils characterized by low shear-wave velocities, high-resolution shear-wave reflection sections can be obtained, with the highest-resolution data related to horizontal or vertical components of motion. Multicomponent recording provides the capacity to record valuable shear-wave velocity information for earthquake amplification and engi-neering investigations in urban environments.

Subsurface investigations in urban areas have to take sealed surfaces and densely built and populated areas into account. The shear-wave reflection seismic system developed at the Leibniz Institute for Applied Geophysics (LIAG) provides a solution for this acquisition technology problem using horizontally polarized shear waves (SH-waves) and noninvasive source and receiver designs.

A seismic reflection survey that was conducted in downtown Boise, Idaho, to help city planners site a new well for injection of spent geothermal water illustrates some methods to safely and successfully employ a seismic reflection survey in an urban setting. The objective of the seismic survey was to estimate the depth and continuity of a basalt and rhyolite volcanic sequence. Well siting was based on geothermal aquifer depth, location of interpreted faults, projected thermal impact of injection on existing wells, surface pipe extension costs, and public land availability. Seismic acquisition tests and careful processing were used to ensure high-quality data while minimizing the potential for damage along city streets. A video camera placed in a sewer and a blast vibration monitor were used to confirm that energy from the seismic source (a 75-in3 land air gun) did not damage nearby buildings, street surfaces, or buried utilities along the survey lines. Walkaway seismic tests were also used to compare signal quality of the air-gun source to an explosive source for imaging targets up to 800 m depth. These tests show less signal bandwidth from the air-gun source compared to the buried explosive source, but the air-gun signal quality was adequate to meet imaging objectives.Seismic reflection results show that the top of this rhyolite/basalt sequence dips (~8-11 ) southwest away from the Boise foothills at depths of 200 to 800 m. Seismic methods enabled interpretation of aquifer depths along the profiles and located fault zones where injected water may encounter fracture permeability and optimally benefit the existing producing system. The acquisition and processing techniques used to locate the Boise injection well may succeed for other hydrogeologic and environmental studies in urban settings.

We propose an innovative workflow based on the complementary use of Rayleigh waves alongside standard P-wave refraction tomography, which better depicts the shallow part of the near-surface P-wave velocity model. Our surface-wave processing sequence led to an S-wave near-surface velocity field that can be used as a constraint for P-wave tomography and can improve P-wave statics determination. Rayleigh waves are processed in three steps. The first step consists of an accurate frequency-dependent traveltime measurement for each selected source-receiver pair in which the phase difference between two adjacent traces is used to derive the phase velocity. Then, a frequency-dependent surface-wave velocity tomography is performed from the picked traveltimes. Finally, after surface-wave tomography, the frequency-dependent phase velocity volume output by the tomography is inverted to deliver an S-wave near-surface velocity model. This model is used to constrain the first-arrival P-wave tomography. To illustrate our method, we use a 3D narrow-azimuth land data set, acquired along a river valley. Strong lateral velocity variations exist in the shallow part, with slow velocities around the unconsolidated sediments of the riverbed and faster velocities in the consolidated sediments of the surrounding hills. A combined first-arrival tomography using the S-wave velocity model, the initial unconstrained refracted P-wave velocity model, and the original first arrivals is used to obtain a more accurate near-surface P-wave velocity model. This new approach led to a constrained P-wave velocity model from which primary statics are derived and then applied, leading to an improved image with better focusing and continuity of thin layers in the shallowest part.

Shear-wave (S-wave) technology has been investigated for about half as long as P-waves as an exploration tool, beginning in the mid-1960s with field experiments and vertical seismic profiles (VSP) to assist interpretation. Although it was immediately recognized that the relative quality of S-wave data was unpredictable, early processing and analysis did not consider the effects of birefringence or splitting. This unpredictable behavior, along with dynamic mis-ties, observed at intersections of 2D lines, was shown in the 1980s to be a result of S-wave splitting in azimuthally anisotropic media. In addition, 20 years of the early effort were devoted to developing S-wave sources. However, ironically, it turned out that conventional P-wave sources were best; P-waves convert to S-wave (PS-wave) reflections at layer interfaces with nearly the same strength as P-wave reflections.

Abstract Over the last 40 years, there has been an expansion of activity in applications of near-surface geophysical techniques for various types of geohazards investigations in Canada; numerous national and international research groups have been working with the Near Surface Geophysics Section of the Geological Survey of Canada to develop techniques for specific Canadian engineering and environmental geohazards problems. A few of the more interesting examples from widespread parts of the country are discussed in this paper.

61A three component MEMS-based seismic landstreamer was developed61Combination with wireless units enables data acquisition in inaccessible areas61Tests show the potential of the system for urban and high-resolution studies61A challenging location from the planned Stockholm Bypass was chosen as a test site61Tomography results show low velocities correspond well to zone of poor quality rock

Pseudorandom vibroseis sweeps have long been suggested as an alternative to standard linear sweeps due to their potential for having superior orthogonality, a lower likelihood for infrastructure damage, and increased low-frequency content. In the past, they were also attractive as they have a better autocorrelation shape, although that is less important today. Their use has been limited but the increasing popularity of simultaneous acquisition techniques has rekindled interest as they offer the ability to reduce interference noise. A wide variety of methods for generating pseudorandom sweeps have been developed over the last 45 years. This paper gives an overview of the motivations for their use before classifying and describing the different sweep types. Finally, the sweeps will be compared in terms of their major attributes including their suitability for simultaneous surveys.

Abstract Optimized pseudo-random sequences proved effective, both theoretically and empirically, in increasing data quality while reducing possible damage to buildings by vibratory sources during seismic reflection data acquisition. The linear sweeps commonly used for vibratory measurements can cause resonance in nearby infrastructure; hence, there is a potential for property damage. A pseudo-random sweep signal can be designed to decrease resonance effects and therefore reduce damage thresholds. The sweep sequences produced by simple random number generators, like the ones given by the vibrator manufacturers, have marked disadvantages, such as high correlation noise, large fluctuations in spectral amplitudes, and reduced seismic energy. To overcome some of these problems, an optimization process can be developed to produce pseudo-random sweeps for site-specific conditions. Two strategies are considered for preprocessing: crosscorrelation and deterministic deconvolution. Analysis of examples for an optimum pseudo-random sweep and simple pseudo-random sweep demonstrates that the total seismic energy is increased, while side-lobe energy is decreased and spectral fluctuations are reduced when the pseudo-random sweep is optimized. A limited-scope field test reveals that the peak particle velocity values are lowered substantially, while correlated and deconvolved records generated by the optimized pseudo-random sweep are of similar quality to a linear-sweep record. Application of optimized pseudo-random sweeps has the potential to increase productivity, while maintaining data quality and reducing resonance in surveys of built-up areas.

AbstractSensing and imaging systems are under increasing pressure to accommodate ever-larger and higher-dimensional data sets; ever-faster capture, sampling, and processing rates; ever-lower power consumption; ever-smaller form factor; and new sensing modalities. These needs have motivated the development of new approaches to signal acquisition and processing. We provide an introduction to the field of compressive sensing (CS), which has stimulated a rethinking of sensor and signal processing system design. In CS, analog signals are digitized and processed not via uniform sampling but via measurements using more general, even random, test functions. In contrast to conventional wisdom, the new theory asserts that one can combine “sub-Nyquist rate sampling” with large-scale optimization for efficient and accurate signal acquisition when the signal has a sparse structure. Particular topics addressed include signal sparsity, randomized sampling, optimization-based signal recovery, and perspectives on applications to seismic data acquisition and processing.

Airborne electromagnetic methods (AEM) are used extensively in groundwater investigations, often in combination with high-resolution seismic data. Despite the frequent use of this mapping strategy, only a few cases are found in the literature. In this study, comparisons and interpretations were made based on AEM (SkyTEM) and high-resolution seismic data from an area covering 10 km 2 in the western part of Denmark. As support for the interpretations, an exploration well was drilled to provide lithological and logging information in the form of resistivity and vertical seismic profiling. Based on the resistivity log, synthetic SkyTEM responses were calculated with a varying number of gate-times in order to illustrate the effect of the noise-level. At the exploration well geophysical data were compared to the lithological log; in general there is good agreement. The same tendency was recognised when SkyTEM results from the area were superposed onto seismic sections. Comprehensive geological knowledge is necessary in order to introduce layer boundaries from one method interactively in the data handling of the other. However, in cases where resistivity transitions are positively correlated to reflections, SkyTEM data supports the interpretation of weak reflections, and can also support the correlation of reflections both internally and between seismic lines. Besides contributing lithological information, the AEM survey provides gross three-dimensional structural information, whereas seismic data contributes with more detailed structural information in two dimensions.

A novel approach, named pQC, was developed to automatically derive near-surface velocities and statics by applying surface-consistent analysis to refraction data, where the data consist of first-break (FB) traveltimes and early-arrival waveforms. This approach is facilitated by the introduction of a new sorting domain in which FB traveltimes and traces are organized in a multidimensional space consisting of a common-midpoint (CMP) location, offset, and azimuth, called the XYOA domain. The FB traveltime data sorted in this domain can be analyzed efficiently with statistical methods to obtain localized average depth domain velocity trends for calculation of long-wavelength statics. Short-wavelength (residual) refraction statics are then calculated based on the cross correlation of early-arrival waveforms in the XYOA gathers over multiple offset classes and inverted for surface-consistent source and receiver corrections. The application of the combined statics solution to the traces enhances the continuity and power of the stacked reflected events without the need to perform tomography. Surface-consistent analysis of refraction data in the XYOA domain is fully automatic, provides robust solutions for noisy data, and enhances subsequent reflection residual statics calculations. This method can also be exploited for quality-control analysis of FB picks and for automating, in an iterative procedure, the picking of large 3D seismic data sets. The method is demonstrated on a 3D land survey over complex geology where the novel refraction surface-consistent solution enhances the imaging results and employs a fraction of the time needed by a typical tomographic workflow.

Geophysical characterization of the subsurface is an integral part of the industry9s effort to decrease ambiguity during exploration, development, and production. Over several decades, advances in geophysical technology (e.g., 3D seismic, AVO, depth imaging, 4D seismic, wide/full azimuth acquisition, etc.) have allowed geophysicists to routinely produce more accurate “best technical case” images of the subsurface. Given the impressive nature of these advances, our nongeophysical colleagues might be tempted to think that geophysicists have eliminated uncertainty from our subsurface images. Nothing could be further from the truth. Most (if not all) of the time, geophysical characterization of the subsurface involves estimating solutions to ill-posed inverse problems. This ill-posedness stems from a variety of sources, including insufficient measurements and physical phenomena like seismic anisotropy.

Shallow shear wave velocities beneath a rock site are characterized using the refraction microtremor (ReMi) technique developed by Louie [Faster, better: shear-wave velocity to 10002m depth from ReMi arrays. Bull Seism Soc Am 2001; 91: 347–64]. Ground motion from a passing train enabled capture of energy propagating parallel to the recording array. This allowed evaluation of the variation of the minimum phase-velocity of the dispersion curve envelope and better estimation of the true minimum velocity beneath the site. We use a new method to image and evaluate the dispersion curve envelope via power–slowness profiles through the slowness–frequency plots introduced by Louie [Faster, better: shear-wave velocity to 10002m depth from ReMi arrays. Bull Seism Soc Am 2001; 91: 347–64]. Data illustrated the frequency dependency of dispersion curve uncertainties, with greater uncertainty occurring at low frequencies. These uncertainties map directly into uncertainty of the inverted velocity–depth profile. Above 10002m depth velocities are well constrained with 10% variability. Variability is greatly reduced when the energy propagation is along the geophone array. Greater velocity variation is observed below 10002m depth.

Subsidence resulting in sinkholes within dissolution mine fields in and around the city of Hutchinson, Kansas, USA (Figure 1) has been reported for more than 90 years. Salt dissolution and the resulting unpredictable upward migration of the dissolution voids can be observed both in proximity to well bores (dissolution mining, brine disposal, and oil wells; seismic shot holes, etc.) and in areas known to experience natural dissolution with no apparent anthropogenic influences. One potential outcome of the upward migration of these long-inactive dissolution voids in the city of Hutchinson is significant structural damage to facilities, infrastructure, or traffic areas. Monitoring the condition of a void9s roof is key to determining and managing this risk. Drilling is expensive for this investigative application in part because of the number of potential targets. At a depth of approximately 120 m, most surface geophysical methods have neither the sensitivity nor resolution necessary to detect these voids, much less interrogate the roof.