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Geophysical monitoring of injected fluids

Description: During injection, a pressure front, fluid front, and thermal front are formed, and move away from the injection well. The performance of a geothermal field is determined by the movement of these fronts through it. The Brine Injection Technology Program is developing modeling and measurement techniques to help industry determine where these fronts are and to predict their evolution. Because these fronts change the physical properties of the reservoir medium as they pass, Lawrence Livermore National Laboratory is studying the application of geophysical methods to provide information about the location of fronts away from observation and sampling wells. The ultimate purpose is to model the behavior of the field and predict its performance. In FY86, we concentrated on collecting microseismicity and electrical self potential data before and after the start-up of a moderate sized geothermal plant. In FY 87, we will complete the analysis of these data sets, and continue collecting case history information.
Date: April 1, 1987
Creator: Kasameyer, P.W.
Partner: UNT Libraries Government Documents Department

Geophysical Measurement of Geothermal Fluid Production and Injection

Description: Geothermal operators use complex reservoir engineering models to design their well fields and production/injection strategies and to predict the performance of their reservoirs. Collection of in-situ data for input and validation of these models in wells is expensive, and geophysical measurements from the surface or remotely at some distance from boreholes can be cost effective. The Hydrothermal Research Program of DOE is developing techniques to track injected fluid and to monitor the effects of production and injection geothermal fields using geophysical means.
Date: January 1, 1988
Creator: Kasameyer, P. W.
Partner: UNT Libraries Government Documents Department

Geothermal programs at Lawrence Livermore National Laboratory

Description: Lawrence Livermore National Laboratory has a number of geothermal programs supported through two offices in the Department of Energy: the Office of Renewable Technologies, Geothermal Technologies Division, and the Office of Basic Energy Sciences, Division of Engineering, Mathematics and Geosciences. Within these programs, we are carrying out research in injection monitoring, optical instrumentation for geothermal wells, seismic imaging methods, geophysical and drilling investigations of young volcanic systems in California, and fundamental studies of the rock and mineral properties.
Date: July 10, 1987
Creator: Kasameyer, P.W. & Younker, L.W.
Partner: UNT Libraries Government Documents Department

High resolution seismic attenuation tomography at Medicine Lake Volcano, California

Description: Medicine Lake Volcano, a broad shield volcano about 50km east of Mount Shasta in northern California, produced rhylotic eruptions as recently as 400 years ago. Because of this recent activity it is of considerable interest to producers of geothermal energy. In a joint project sponsored by the Geothermal Research Program of the USGS and the Division of Geothermal and Hydropower Division of the US-DOE, the USGS and LLNL conducted an active seismic experiment designed to explore the area beneath and around the caldera. The experiment of eight explosions detonated in a 50 km radius circle around the volcano recorded on a 11 x 15 km grid of 140 seismographs. The travel time data from the experiment have been inverted for structure and are presented elsewhere in this volume. In this paper we present the results of an inversion for 1/Q structure using t* data in a modified Aki inversion scheme. Although the data are noisy, we find that in general attenuative zones correlate with low velocity zones. In particular, we observe a high 1/Q zone roughly in the center of the caldera at 4 km depth in between two large recent dacite flows. This zone could represent the still molten or partially molten source of the flows.
Date: July 10, 1987
Creator: Zucca, J.J. & Kasameyer, P.W.
Partner: UNT Libraries Government Documents Department

Thermal depletion of a geothermal reservoir with both fracture and pore permeability

Description: A method for estimating the useful lifetime of a reservoir in porous rock where the injection and production wells intersect a fracture system is presented. Equations were derived for the pore-fluid and fracture-fluid temperatures averaged over large regions of the geothermal field. Problems such as incomplete areal sweep and interfingering of cool and hot fluids are ignored. Approximate equations relating average temperatures to the heat flowing from rock to fluid were developed, and their use is justified by comparing the results with solutions of the exact equations. The equations for the temperature decline can be solved quickly. In the model, fractures are characterized by three parameters: aperture w, permeability k/sub fr/, and spacings between fractures D. For certain values of these parameters, cool reinjected fluid in fractures may reach the production wells long before all the warm pore fluid has been tapped, shortening the useful lifetime of the field. The traditional (and important) problems of reservoir engineering, flow rate determination, drawdown, sweep patterns, etc. were ignored. Thus the results are most useful in providing a correction factor which can be applied to lifetime estimates obtained from a detailed simulation of a field assuming porous rock. That correction factor is plotted for clean fractures (k/sub fr/ = w/sup 2//12) as a function of w and D for several lifetime ranges. Small-scale fractures seen in cores from the Salton Sea Geothermal Field are too closely spaced to reduce lifetime estimates. However, large-scale fault systems exist within that field, and they are attractive drilling targets because they produce large flow rates. If large scale faults communicate between injection and production wells, they may reduce the useful lifetime of those wells.
Date: August 10, 1976
Creator: Kasameyer, P.W. & Schroeder, R.C.
Partner: UNT Libraries Government Documents Department

Application of Thermal Depletion Model to Geothermal Reservoirs with Fracture and Pore Permeability

Description: The useful lifetime of a geothermal resource is usually calculated by assuming fluid will be produced from and reinjected into a uniform porous medium. However, most geothermal systems are found in fractured rock. If the reinjection and production wells intersect connected fractures, then reinjected fluid may cool the production wells much sooner than would be predicted from calculations of flow in a porous medium. We have developed a “quick and dirty” method for calculating how much sooner that cooling will occur (Kasameyer and Schroeder, 1975, 1976). In this paper, we discuss the basic assumptions of the method, and show how it can be applied to the Salton Geothermal Field, the Raft River System, and to reinjection of supersaturated fluids. 6 refs., 6 figs.
Date: December 1, 1976
Creator: Kasameyer, P.W. & Schroeder, R.C.
Partner: UNT Libraries Government Documents Department

Borehole Gravity Measurements In The Salton Sea Scientific Drilling Program Well State 2-14

Description: Borehole gravity measurements over a depth range from 1737 to 1027 m, and the vertical gradient of gravity were measured at the Salton Sea Scientific Drilling Program well State 2-14. The borehole gravimetric densities matched the well logs, but the surface gradient was found to be 0.0040 mgal/m higher than expected. When the borehole observations are corrected for the observed free air gradient above ground, they produce densities which are nearly uniformly higher than log densities by about 0.07 gm/cm{sup 3}. These measurements require densities in the depth range .5 to 3 km, for a radius of a few kilometers around State 2-14 to be as dense as those found in State 2-14. Combining the borehole gravity and calculated vertical gravity gradients on the surface, we find that this densified zone covers much of a broad thermal anomaly to the northeast of the Salton Sea Geothermal Field.
Date: January 1, 1987
Creator: Kasameyer, P. W. & Hearst, J. R.
Partner: UNT Libraries Government Documents Department

Borehole Gravity Measurements in the Salton Sea Scientific Drilling Program Well State 2-14

Description: Borehole gravity measurements over a depth range from 1737 to 1027 m, and the vertical gradient of gravity above ground were measured at the Salton Sea Scientific Drilling Program well State 2-14. Uncorrected borehole gravimetric densities match values from gamma-gamma logs, indicating that the high densities seen in State 2-14 in the depth range 0.5 to 3 km extend for a few kilometers from the well. The above-ground gradient was found to be 0.0040 mgal/m higher than expected; correcting for this value increases the gravimetric density in the borehole. Combining the borehole gravity and estimated vertical gravity gradients on the surface, they find that this densified zone coincides with much of a broad thermal anomaly that has been found to the northeast of the Salton Sea Geothermal Field.
Date: January 1, 1988
Creator: Kasameyer, P. W. & Hearst, J. R.
Partner: UNT Libraries Government Documents Department

Borehole Gravity Measurements in the Salton Sea Scientific Drilling Program Well State 2-14

Description: Borehole gravity measurements over a depth range from 1737 to 1027 m, and the vertical gradient of gravity above ground were measured at the Salton Sea Scientific Drilling Program well State 2-14. Uncorrected borehole gravimetric densities match values from gamma-gamma logs, indicating that the high densities seen in State 2-14 in the depth range 0.5 to 3 km extend for a few kilometers from the well. The above-ground gradient was found to be 4.1 {micro}gal/m higher than expected; correcting for this value increases the gravimetric density in the borehole. Combining the borehole gravity and estimated vertical gravity gradients on the surface, they find that this densified zone coincides with much of a broad thermal anomaly that has been found to the northeast of the Salton Sea Geothermal Field.
Date: January 1, 1988
Creator: Kasameyer, P. W. & Hearst, J. R.
Partner: UNT Libraries Government Documents Department

Deep Structure Of Long Valley, California, Based On Deep Reflections From Earthquakes

Description: Knowledge of the deep structure of Long Valley comes primarily from seismic studies. Most of these efforts have focused on delimiting the top of the inferred magma chamber. We present evidence for the location of the bottom of the low velocity layer (LVL). Two other studies have provided similar information. Steeples and Iyer (1976) inferred from teleseismic P-wave delays that low-velocity material extends from 7 km depth to 25 to 40 km, depending on the velocities assumed. Luetgert and Mooney (1985) have examined seismic refraction data from earthquake sources and have identified a reflection that appears to be from the lower boundary of a magma chamber. They detected the reflection with a linear array of single component stations, and assuming it traveled in a vertical plane, matched the travel time and apparent velocity (6.3 km/sec) to deduce that it was a P-P reflection from within a LVL. We recorded a similar phase with a 2-dimensional array of three-component stations, and carried out a similar analysis, but utilized additional information about the travel path, particle motions and amplitudes to constrain our interpretation. Our data comes from a passive seismic refraction experiment conducted during August 1982. Fourteen portable seismograph stations were deployed in a network with approximately 5 km station spacing in the Mono Craters region north of Long Valley (Figure 1). The network recorded earthquakes located south of Long Valley and in the south moat. Three components of motion were recorded at all sites. The data represent one of the few times that three-component data has been collected for raypaths through a magma chamber in the Long Valley area.
Date: January 1, 1987
Creator: Zucca, J. J. & Kasameyer, P. W.
Partner: UNT Libraries Government Documents Department

Interpretation of Self-Potential Anomalies Using Constitutive Relationships for Electrochemical and Thermoelectric Coupling Coefficients

Description: Constitutive relationships for electrochemical and thermoelectric cross-coupling coefficients are derived using ionic mobilities, applying a general derivative of chemical potential and employing the zero net current condition. The general derivative of chemical potential permits thermal variations which give rise to the thermoelectric effect. It also accounts for nonideal solution behavior. An equation describing electric field strength is similarly derived with the additional assumption of electrical neutrality in the fluid Planck approximation. The Planck approximation implies that self-potential (SP) is caused only by local sources and also that the electric field strength has only first order spatial variations. The derived relationships are applied to the NaCl-KCl concentration cell with predicted and measured voltages agreeing within 0.4 mV. The relationships are also applied to the Long Valley and Yellowstone geothermal systems. There is a high degree of correlation between predicted and measured SP response for both systems, giving supporting evidence for the validity of the approach. Predicted SP amplitude exceeds measured in both cases; this is a possible consequence of the Planck approximation. Electrochemical sources account for more than 90% of the predicted response in both cases while thermoelectric mechanisms account for the remaining 10%; electrokinetic effects are not considered. Predicted electrochemical and thermoelectric voltage coupling coefficients are comparable to values measured in the laboratory. The derived relationships are also applied to arbitrary distributions of temperature and fluid composition to investigate the geometric diversity of observed SP anomalies. Amplitudes predicted for hypothetical saline spring and hot spring environments are less than 40 mV. In contrast, hypothetical near surface steam zones generate very large amplitudes, over 2 V in one case. These results should be viewed with some caution due to the uncertain validity of the Planck approximation for these conditions. All amplitudes are controlled by electrochemical mechanisms. Polarities are controlled by the ...
Date: January 1, 1988
Creator: Knapp, R. B. & Kasameyer, P. W.
Partner: UNT Libraries Government Documents Department

Preliminary report on shallow research drilling in the Salton Sea region

Description: During two shallow thermal drilling programs, thermal measurements were obtained in 56 shallow (76.2 m) and one intermediate (457.3 m) depth holes located both onshore and offshore along the southern margin of the Salton Sea in the Imperial Valley, California. These data complete the surficial coverage of the thermal anomaly, revealing the shape and lateral extent of the hydrothermal system. The thermal data show the region of high thermal gradients to extend only a short distance offshore to the north of the Quaternary volcanic domes which are exposed along the southern shore of the Salton Sea. The central thermal anomaly has an arcuate shape, about 4 km wide and 12 km long. Across the center of the anomaly, the transition zone between locations exhibiting high thermal gradients and those exhibiting regional thermal gradients is quite narrow. Thermal gradients rise from near regional (0.09/degree/C/m) to extreme (0.83/degree/C/m) in only 2.4 km. The heat flow in the central part of the anomaly is greater than 600 mW/m/sup 2/ and in some areas exceeds 1200 mW/m/sup 2/. The shape of the thermal anomaly is asymmetric with respect to the line of volcanoes previously thought to represent the center of the field, with its center line offset south of the volcanic buttes. There is no broad thermal anomaly associated with the magnetic high that extends offshore to the northeast from the volcanic domes.
Date: January 14, 1988
Creator: Newmark, R.L.; Kasameyer, P.W. & Younker, L.W.
Partner: UNT Libraries Government Documents Department

Method of using in situ porosity measurements to place an upper bound on geothermal reservoir compaction

Description: Placing an upper bound on reservoir compaction requires placing a lower bound on the reservoir effective compaction modulus. Porosity-depth data can be used to find that lower-bound modulus in a young sedimentary basin. Well-log and sample porosity data from a geothermal field in the Imperial Valley, CA, give a lower-bound modulus of 7.7 x 10{sup 3} psi. This modulus is used with pressure drops calculated for a reservoir to determine an upper bound on reservoir compaction. The effects of partial reinjection and aquifer leakage on upper-bound subsidence estimated from the compaction are illustrated for a hypothetical reservoir and well array.
Date: January 3, 1979
Creator: Schatz, J.F.; Kasameyer, P.W. & Cheney, J.A.
Partner: UNT Libraries Government Documents Department

Calibration of a neutron log in partially saturated media. Part II. Error analysis

Description: Four sources or error (uncertainty) are studied in water content obtained from neutron logs calibrated in partially saturated media for holes up to 3 m. For this calibration a special facility was built and an algorithm for a commercial epithermal neutron log was developed that obtains water content from count rate, bulk density, and gap between the neutron sonde and the borehole wall. The algorithm contained errors due to the calibration and lack of fit, while the field measurements included uncertainties in the count rate (caused by statistics and a short time constant), gap, and density. There can be inhomogeneity in the material surrounding the borehole. Under normal field conditions the hole-size-corrected water content obtained from such neutron logs can have an uncertainty as large as 15% of its value.
Date: March 20, 1981
Creator: Hearst, J.R.; Kasameyer, P.W. & Dreiling, L.A.
Partner: UNT Libraries Government Documents Department

Potential uses for a high-temperature borehole gravimeter

Description: It is possible to design a canister to cool a borehole gravimeter for use in geothermal and high-temperature (up to 350/sup 0/C) gas wells. Repeat surveys with such a gravimeter could (1) help estimate the extent of reservoir plugging in geothermal injection well after one year of operation and (2) detect compaction of a geothermal aquifer if the change in thickness of the aquifer exceeds 1 m. The instrument could be used together with conventional logging tools to evaluate radial dependence of density around a well, or to estimate gas-filled porosity around wells drilled with mud. A high-temperature borehole gravimeter could also be used to evaluate structure and stratigraphy around geothermal and high-temperature gas wells.
Date: March 8, 1978
Creator: Hearst, J.R.; Kasameyer, P.W. & Owen, L.B.
Partner: UNT Libraries Government Documents Department

Seismic imaging of the Medicine Lake Caldera

Description: Medicine Lake Volcano, a broad shield volcano about 50 km east of Mount Shasta in northern California, produced rhylotic eruptions as recently as 400 years ago. Because of this recent activity it is of considerable interest to producers of geothermal energy. The USGS and LLNL conducted an active seismic experiment designed to explore the area beneath and around the caldera. This experiment had two purposes: To produce high-quality velocity and attenuation images of the young magma body presumed to be the source for the young volcanic features, and to collect a dataset that can be used to develop and test seismic imaging methods that may be useful for understanding other geothermal systems. Eight large explosions were detonated in a 50 km radius circle around the volcano, a distance chosen to produce strong upward traveling signals through the area of interest. The data were inverted using Aki's method to produce three-dimensional velocity and attenuation images of the sub-surface. Preliminary interpretation shows low velocity and attenuation on the flanks of the volcano, and coincident high attenuation values and low velocities (-20%) from 3 to 5 km beneath the center of the caldera. This zone may be a region of partial melt which fed the youngest eruptions.
Date: April 1, 1987
Creator: Zucca, J.J.; Evans, J.R. & Kasameyer, P.W.
Partner: UNT Libraries Government Documents Department

Geological, Geophysical, And Thermal Characteristics Of The Salton Sea Geothermal Field, California

Description: The Salton Sea Geothermal Field is the largest water-dominated geothermal field in the Salton Trough in Southern California. Within the trough, local zones of extension among active right-stepping right-lateral strike-slip faults allow mantle-derived magmas to intrude the sedimentary sequence. The intrusions serves as heat sources to drive hydrothermal systems. We can characterize the field in detail because we have an extensive geological and geophysical data base. The sediments are relatively undeformed and can be divided into three categories as a function of depth: (1) low-permeability cap rock, (2) upper reservoir rocks consisting of sandstones, siltstones, and shales that were subject to minor alterations, and (3) lower reservoir rocks that were extensively altered. Because of the alteration, intergranular porosity and permeability are reduced with depth. permeability is enhanced by renewable fractures, i.e., fractures that can be reactivated by faulting or natural hydraulic fracturing subsequent to being sealed by mineral deposition. In the central portion of the field, temperature gradients are high near the surface and lower below 700 m. Surface gradients in this elliptically shaped region are fairly constant and define a thermal cap, which does not necessarily correspond to the lithologic cap. At the margin of the field, a narrow transition region, with a low near-surface gradient and an increasing gradient at greater depths, separates the high temperature resource from areas of normal regional gradient. Geophysical and geochemical evidence suggest that vertical convective motion in the reservoir beneath the thermal cap is confined to small units, and small-scale convection is superimposed on large-scale lateral flow of pore fluid. Interpretation of magnetic, resistivity, and gravity anomalies help to establish the relationship between the inferred heat source, the hydrothermal system, and the observed alteration patterns. A simple hydrothermal model is supported by interpreting the combined geological, geophysical, and thermal data. In the ...
Date: January 1, 1981
Creator: Younker, L.W.; Kasameyer, P. W. & Tewhey, J. D.
Partner: UNT Libraries Government Documents Department

Predicting the Rate by which Suspended Solids Plug Geothermal Injection Wells

Description: Standard membrane filtration tests have been used by the oil industry for more than 20 years to evaluate injection well performance. Published analytical models are also available fore relating filtration data to injector lifetimes. We have utilized these techniques to evaluate injection at the Salton Sea Geothermal Field, Southern California. Results indicate that direct injection into reservoir zones with primary porosity is not feasible unless 1-micrometer or larger particulates formed during or after the energy conversion process are removed. Membrane filter tests are useful in evaluating injectivity of geothermal effluents. Techniques are available for estimating injector half-life utilizing filtration data. Injection of brine with suspended solids is not feasible in reservoir zones with primary porosity. However, long-term injection of brine and suspended solids can apparently be achieved in fracture zones. 1 tab., 3 figs., 12 refs.
Date: December 14, 1977
Creator: Owen, L.B.; Kasameyer, P.W.; Netherton, R. & Thorson, L.
Partner: UNT Libraries Government Documents Department

Velocity and Attenuation Structure of the Geysers Geothermal Field, California

Description: The Geysers geothermal field is located in northern California and is one of the world's largest producers of electricity from geothermal energy. The resource consists of primarily dry steam which is produced from a low, porosity fractured graywacke. Over the last several years steam pressure at the Geysers has been dropping. Concern over decline of the resource has prompted research to understand its fundamental nature. A key issue is the distribution of fluid in the matrix of the reservoir rock. In this paper we interpret seismic compressional-wave velocity and attenuation data at the Geysers in terms of the geologic structure and fluid saturation in the reservoir. Our data consist of approximately 300 earthquakes that are of magnitude 1.2 and are distributed in depth between sea level and 2.5 km. Using compressional-wave arrival times, we invert for earthquake location, origin time, and velocity along a three-dimensional grid. Using the initial pulse width of the compressional-wave, we invert for the initial pulse width associated with the source, and the one-dimensional Q structure. We find that the velocity structure correlates with known mapped geologic units, including a velocity high that is correlated with a felsite body at depth that is known from drilling. The dry steam reservoir, which is also known from drilling, is mostly correlated with low velocity. The Q increases with depth to the top of the dry steam reservoir and decreases with depth within the reservoir. The decrease of Q with depth probably indicates that the saturation of the matrix of the reservoir rock increases with depth.
Date: January 1, 1993
Creator: Zucca, J. J.; Hutchings, L. J. & Kasameyer, P. W.
Partner: UNT Libraries Government Documents Department

Shallow Drilling In The Salton Sea Region, The Thermal Anomaly

Description: During two shallow thermal drilling programs, thermal measurements were obtained in 56 shallow (76.2 m) and one intermediate (457.3 m) depth holes located both onshore and offshore along the southern margin of the Salton Sea in the Imperial Valley, California. These data complete the surficial coverage of the thermal anomaly, revealing the shape and lateral extent of the hydrothermal system. The thermal data show the region of high thermal gradients to extend only a short distance offshore to the north of the Quaternary volcanic domes which are exposed along the southern shore of the Salton Sea. The thermal anomaly has an arcuate shape, about 4 km wide and 12 km long. Across the center of the anomaly, the transition zone between locations exhibiting high thermal gradients and those exhibiting regional thermal gradients is quite narrow. Thermal gradients rise from near regional (0.09 C/m) to extreme (0.83 C/m) in only 2.4 km. The heat flow in the central part of the anomaly is >600 mW/m{sup 2} and in some areas exceeds 1200 mW/m{sup 2}. The shape of the thermal anomaly is asymmetric with respect to the line of volcanoes previously thought to represent the center of the field, with its center line offset south of the volcanic buttes. There is no broad thermal anomaly associated with the magnetic high that extends offshore to the northeast from the volcanic domes. These observations of the thermal anomaly provide important constraints for models of the circulation of the hydrothermal system. Thermal budgets based on a simple model for this hydrothermal system indicate that the heat influx rate for local ''hot spots'' in the region may be large enough to account for the rate of heat flux from the entire Salton Trough.
Date: January 1, 1987
Creator: Newmark, R. L.; Kasameyer, P. W. & Younker, L. W.
Partner: UNT Libraries Government Documents Department

Independent seismic evaluation of the 24-580-980 south connector ramps

Description: The interchange for highways 24, 580, and 980 (the Stack) in Oakland, California, lies 4.3 km from the surface expression of the Hayward fault and 26 km from the San Andreas fault. The purpose of this project is to compute realistic, linear, strong ground motion (rock outcrop motion) likely to affect this interchange during a hazardous earth-quake on the Hayward fault. With the exception of very long period ( >20 sec) motion, the Hayward fault will be the controlling deterministic ground motion hazard to this structure. We identified a magnitude M = 7.25 earthquake that ruptures 82 km of the Hayward fault as the principal hazard to the Stack; it has a moment of 8.5 x 10{sup 26} dyne-cm. Moment magnitudes (Hanks and Kanamori, 1979) are used in this report. Our goal is to produce realistic synthesized ground motion for three components and the full wavetrain and for frequencies from 0.05 to 33.0 Hz.
Date: May 1, 1997
Creator: Hutchings, L.J.; Kasameyer, P.W.; Jarpe, S.P. & Foxall, W.
Partner: UNT Libraries Government Documents Department

36Cl/Cl ratios in geothermal systems: preliminary measurements from the Coso Field

Description: The {sub 36}Cl/Cl isotopic composition of chlorine in geothermal systems can be a useful diagnostic tool in characterizing hydrologic structure, in determining the origins and age of waters within the systems, and in differentiating the sources of chlorine (and other solutes) in the thermal waters. The {sub 36}Cl/Cl values for several geothermal water samples and reservoir host rock samples from the Coso, California geothermal field have been measured for these purposes. The results indicate that most of the chlorine is not derived from the dominant granitoid that host the geothermal system. If the chlorine was originally input into the Coso subsurface through meteoric recharge, that input occurred at least 1-1.25 million years ago. The results suggest that the thermal waters could be connate waters derived from sedimentary formations, presumably underlying and adjacent top the granitic rocks, which have recently migrated into the host rocks. Alternatively, most of the chlorine but not the water, may have recently input into the system from magmatic sources. In either case, the results indicate that most of the chlorine in the thermal waters has existed within the granitoid host rocks for no more than about 100,00-200,00 years. this residence time for the chlorine is similar to residence times suggested by other researchers for chlorine in deep groundwaters of the Mono Basin north of the Coso field.
Date: July 1, 1997
Creator: Nimz, G.J.; Moore, J.N. & Kasameyer, P.W.
Partner: UNT Libraries Government Documents Department

Synthetic strong ground motions for engineering design utilizing empirical Green`s functions

Description: We present a methodology for developing realistic synthetic strong ground motions for specific sites from specific earthquakes. We analyzed the possible ground motion resulting from a M = 7.25 earthquake that ruptures 82 km of the Hayward fault for a site 1.4 km from the fault in the eastern San Francisco Bay area. We developed a suite of 100 rupture scenarios for the Hayward fault earthquake and computed the corresponding strong ground motion time histories. We synthesized strong ground motion with physics-based solutions of earthquake rupture and applied physical bounds on rupture parameters. By having a suite of rupture scenarios of hazardous earthquakes for a fixed magnitude and identifying the hazard to the site from the statistical distribution of engineering parameters, we introduce a probabilistic component into the deterministic hazard calculation. Engineering parameters of synthesized ground motions agree with those recorded from the 1995 Kobe, Japan and the 1992 Landers, California earthquakes at similar distances and site geologies.
Date: April 11, 1996
Creator: Hutchings, L. J.; Jarpe, S. P.; Kasameyer, P. W. & Foxall, W.
Partner: UNT Libraries Government Documents Department

Seismic monitoring of a flow test in the Salton Sea Geothermal Field

Description: The purpose of this seismic monitoring project was to characterize in detail the micro-seismic activity related to the flow-injection test in the Salton Sea Geothermal Field. Our goal was to determine if any sources of seismic energy related to the test were observable at the surface, using both conventional seismic network techniques and relatively newer array techniques. These methods allowed us to detect and locate both impulsive microearthquakes and continuous sources of seismic energy. Our network, which was sensitive enough to be triggered by magnitude 0.0 or larger events, found no impulsive microearthquakes in the vicinity of the flow test in the 8 month period before the test and only one event during the flow test. We have observed some continuous seismic noise sources that may be attributed to the flow test. 4 refs., 4 figs.
Date: June 1, 1989
Creator: Jarpe, S.P.; Kasameyer, P.W. & Johnston, C.
Partner: UNT Libraries Government Documents Department