Fault imaging in sparsely sampled 3D seismic data using common‐reflection‐surface processing and attribute analysis – a study in the Upper Rhine Graben     

Hermann A. Buness  Hartwig von Hartmann  Hanna‐Maria Rumpel  Charlotte M. Krawczyk  Rüdiger Schulz 《Geophysical Prospecting》2014,62(3):443-452

Cost reduction in seismic reconnaissance is an issue in geothermal exploration and can principally be achieved by sparse acquisition. To address the adherent decrease in signal/noise ratio, the common‐reflection‐surface method has been proposed. We reduced the data density of an existing 3D dataset and evaluated the results of common‐reflection‐surface processing using seismic attributes. The application of the common‐reflection‐surface method leads in all cases to an improvement of the signal/noise ratio. The most distinct improvement can be seen in the low fold regions. The improvement depends strongly on the midpoint aperture, and there is a tradeoff between reflector continuity and horizontal resolution. If small scale targets are to be imaged, a small aperture size is necessary, which may be far below the Fresnel zone for a specific reflector. The substantial reduction of the data density leads in our case to an irrecoverable information loss.  相似文献   

Acceptance criteria for urban dispersion model evaluation     

Steven Hanna  Joseph Chang 《Meteorology and Atmospheric Physics》2012,116(3-4):133-146

The authors suggested acceptance criteria for rural dispersion models’ performance measures in this journal in 2004. The current paper suggests modified values of acceptance criteria for urban applications and tests them with tracer data from four urban field experiments. For the arc-maximum concentrations, the fractional bias should have a magnitude <0.67 (i.e., the relative mean bias is less than a factor of 2); the normalized mean-square error should be <6 (i.e., the random scatter is less than about 2.4 times the mean); and the fraction of predictions that are within a factor of two of the observations (FAC2) should be >0.3. For all data paired in space, for which a threshold concentration must always be defined, the normalized absolute difference should be <0.50, when the threshold is three times the instrument’s limit of quantification (LOQ). An overall criterion is then applied that the total set of acceptance criteria should be satisfied in at least half of the field experiments. These acceptance criteria are applied to evaluations of the US Department of Defense’s Joint Effects Model (JEM) with tracer data from US urban field experiments in Salt Lake City (U2000), Oklahoma City (JU2003), and Manhattan (MSG05 and MID05). JEM includes the SCIPUFF dispersion model with the urban canopy option and the urban dispersion model (UDM) option. In each set of evaluations, three or four likely options are tested for meteorological inputs (e.g., a local building top wind speed, the closest National Weather Service airport observations, or outputs from numerical weather prediction models). It is found that, due to large natural variability in the urban data, there is not a large difference between the performance measures for the two model options and the three or four meteorological input options. The more detailed UDM and the state-of-the-art numerical weather models do provide a slight improvement over the other options. The proposed urban dispersion model acceptance criteria are satisfied at over half of the field experiments.  相似文献   

Changes in Nutrient and Carbon Availability and Temperature as Factors Controlling Bacterial Growth in the Northern Baltic Sea   总被引：1，自引：0，他引：1  

Laura Hoikkala  Hanna Aarnos  Risto Lignell 《Estuaries and Coasts》2009,32(4):720-733

The effects of inorganic nutrient (N and P) and glucose C treatments on bacterial growth were followed for 3 days in natural surface and deep water bacterial samples during the main post-spring bloom stages of phytoplankton growth in the northern Baltic Sea. In addition, the importance of photochemical degradation of dissolved organic matter on bacterial growth was investigated vertically (0.1–2.0 m) and spatially, in a salinity gradient from river mouth to open sea. Bacterial production was consistently C limited in the surface layer, with N or both N and P as the secondary limiting nutrients from spring to early summer and in late summer, respectively. In deep water, bacterial growth showed combined temperature and C limitation, and in spring, this also appeared to be true with surface samples. The effect of 1-day sunlight pre-treatment varied from no effect up to a 44% production increase, with clear bacterial production responses only being seen at the surface (10 cm depth). The implications of bacterial C limitation for the structure and function of the surface plankton ecosystem, including its CO₂ exchange with the atmosphere are discussed.  相似文献   

Efficient mode superposition algorithm for seismic analysis of non-linear structures     

Roberto Villaverde  Melad M. Hanna 《地震工程与结构动力学》1992,21(10):849-858

A step-by-step integration method is proposed to compute within the framework of the conventional mode superposition technique the response of bilinear hysteretic structures subjected to earthquake ground motions. The method is computationally efficient because only a few modes are needed to obtain an accurate estimate of such a response, and because it does not require the use of excessively small time steps to avoid problems of accuracy or stability. It is developed on the basis that the non-linear terms in the equations of motion for non-linear systems may be considered as additional external forces, and the fact that by doing so such equations of motion can be interpreted as the equations of motion of an equivalent linear system, excited by a modified ground motion. These linear equations are then subjected to a conventional modal decomposition and transformed, as with linear systems, into a set of independent differential equations, each representing the system's response in one of its modes of vibration. To increase the efficiency of the method and account properly for the participation of higher modes, these independent equations are solved using the Nigam-Jennings technique in conjunction with the so-called mode acceleration method. The accuracy and efficiency of the method is verified by means of a comparative study with solutions obtained with a conventional direct integration method. In this comparative study, including only a few modes, the proposed method accurately predicts the seismic response of three two-dimensional frame structures, but requiring only, on an average, about 47 per cent less computer time than when the direct integration method is used.  相似文献   

Diurnal variation of horizontal wind direction fluctuations in complex terrain at Geysers,Cal.     

Steven R. Hanna 《Boundary-Layer Meteorology》1981,21(2):207-213

Horizontal diffusion in the surface layer is dependent on the standard deviation of wind direction fluctuations . Diurnal variation of this parameter in complex terrain was studied for the July 1979 Geysers, Cal., experiment using data from a network of 11 short meteorological towers in the 25 km² Anderson Creek watershed Valley side slopes are roughly 20 ° and maximum terrain difference is about 1 km.Values of for wind directions sampled for one hour at a height of 10 m are about 35 ° during the daytime. They slowly decrease to about 20 ° by 8 to 10 p.m. as stability increases but wind speeds are still relatively high. After 10 p.m. the drainage flow sets in at most stations, with speeds of 1 to 2 m s^-1, and average increases to about 30° during the period 11 p.m. to 6 a.m. In general, highest values of at night are associated with lowest values of wind speed and greatest static stability. This enhancement of by the terrain suggests that horizontal diffusion at night always conforms to that expected during nearly neutral stabilities. That is, Pasquill class D diffusion applies to the horizontal component all night in complex terrain.  相似文献   

Array filters for sidelobe elimination     

Hanna  M. Simaan  M. 《Oceanic Engineering, IEEE Journal of》1985,10(3):248-254

The response of an array of sensors to coherent undesired noise interfering with the measurement of a desired signal can be optimized if special filters are applied to the outputs of the sensors. In this paper, we derive analytic expressions for filters which minimize the power spectrum of the array response to the undesired coherent signal while simultaneously providing an all-pass condition for the desired signal. These filters are shown to yield an array rejection response which has zero-width main lobes and no sidelobes. An example illustrating the results is also presented.  相似文献   

Advanced techniques in site characterization and mining hazard detection for the underground coal industry     

David R. Hanson  Thomas L. Vandergrift  Matthew J. DeMarco  Kanaan Hanna 《International Journal of Coal Geology》2002,50(1-4)

Today's highly productive coal mining systems represent large capital investments. Careful geotechnical planning and design are essential to protect these systems and to help ensure their overall success. Too often, however, the ability of the mine operator to adequately characterize the geotechnical environment and keep up with changing geologic conditions lags the advance rate of the mining equipment. Seismic tomographic imaging, based on the same principles as medical Computer-Aided-Tomography (CAT) Scans, offers the ability to identify changing geologic conditions, loading patterns, and the location of nearby abandoned mine workings. Although seismic tomography has been used for many years in the oil industry, until recently its practicality in the mining industry has been limited because the processes involved interfered with mining productivity and were labor-intensive in terms of data collection and interpretation. New advancements in signal processing have greatly enhanced the speed, resolution, and range of applications of tomographic imaging in underground coal mine settings.Many tomography applications in the mining industry use seismic velocity and/or attenuation tomography within a volume enclosed by the seismic source and receiver array. Although results obtained using this geometry work well in many situations, recent developments in reflection tomography show promise in eliminating the requirement that the target volume be surrounded by sources/receivers. For example, in-seam seismic reflection tomography may now be used to image structures and/or old workings from one general location in the mine (e.g., face areas of mains and panel developments) well ahead of planned developments—largely eliminating the need to probe-hole drill on regular intervals. These new developments have greatly expanded the ability of the mine operator to cost-effectively characterize previously inaccessible areas of the property.This paper gives an overview of the theories and processes involved in seismic tomography applicable to coal mine settings. Recent examples are presented of tomographic imaging applied to a variety of coal mine ground control problems and old works detection in the United States and Europe. The applicability of both seismic refraction and seismic reflection tomography is discussed.  相似文献   

The effect of line averaging on concentration fluctuations     

Steven R. Hanna 《Boundary-Layer Meteorology》1987,40(4):329-338

The reduction in variance of concentration fluctuations due to line averaging is estimated assuming that the process is influenced by the integral distance scale, y _I , of ambient turbulence and the scaling width, W, of the time-averaged plume. An analytical formula is derived for the line-averaged variance for situations where the autocorrelogram is exponential and the point variance decreases exponentially with distance from plume centerline. Predictions of concentration fluctuation variance are compared with water tank and field data, with the result that the decrease of variance with averaging distance is well-simulated if the model parameters y _I and W are carefully chosen.  相似文献   

An empirical formula for the height of the coastal internal boundary layer     

Steven R. Hanna 《Boundary-Layer Meteorology》1987,40(1-2):205-207

Observations of the height of the daytime coastal internal boundary layer at several sites are used to justify an empirical formula in the Offshore and Coastal Dispersion (OCD) model, which states that the boundary-layer slope is 0.1 in the first 2km from the shoreline, and 0.03 therafter.  相似文献   

The exponential probability density function and concentration fluctuations in smoke plumes     

Steven R. Hanna 《Boundary-Layer Meteorology》1984,29(4):361-375

Observations of 1-s average concentration fluctuations during two trials of a U.S. Army diffusion experiment are presented and compared with model predictions based on an exponential probability density function (pdf). The source is near the surface and concentration monitors are on lines about 30 to 100 m downwind of the source. The observed ratio of the standard deviation to the mean of the concentration fluctuations is about 1.3 on the mean plume axis and 4 to 5 on the mean plume edges. Plume intermittency (fraction of non-zero readings) is about 50%; on the mean plume axis and 10%; on the mean plume edges. A meandering plume model is combined with an exponential pdf assumption to produce predictions of the intermittency and the standard deviation of the concentration fluctuations that are within 20%; of the observations.  相似文献