Imperial Valley Research Articles

Apparent horizontal propagation velocity for the 1979 imperial valley earthquake : O'Rourke, M J; Dobry, R Bull Seismol Soc Am, V72, N6, Part A, Dec 1982, P2377–2380

Apparent horizontal propagation velocity for the 1979 imperial valley earthquake : O'Rourke, M J; Dobry, R Bull Seismol Soc Am, V72, N6, Part A, Dec 1982, P2377–2380

Local variations of seismic velocity in the imperial valley, California

We inverted local earthquake arrival times to estimate spatial variations of seismic velocity. Our model consisted of near-surface station corrections and local perturbations to a standard crustal velocity model. We found a zone of relatively high-velocity trending southeast from the Salton Sea. This zone corresponds to the region of thickest sediments. We compared our results with those of teleseismic studies by Savino et al. (1977). The agreement was excellent, suggesting that the teleseismic delays are caused primarily by crustal velocity variations. Residual delays between the teleseismic observations and predicted crustal delays imply crustal thinning of 3 or 4 km along the axis of the valley. Known geothermal resource areas at Salton Sea (or Obsidian Buttes), Brawley, and East Mesa, lie on the axis of a zone of thin crust, and they may be intimately related to the Brawley fault. The crust beneath these areas may be locally even thinner than elsewhere along the Imperical Valley trough, or the crust may have locally higher seismic velocities, or both. Neither local earthquake nor teleseismic arrival times can discriminate between these hypotheses, but the issue might be resolved by combining both types of data. Known geothermal resource areas at Heber, Dunes, and Glamis, lie away from the projected trace of the Brawley fault. These areas are nearly aseismic, and overlie crust with apparent seismic velocities only mildly higher than the regional average. These apparent velocity anomalies could be related to crustal thinning, but because of the very mild Bouguer gravity anomalies in these areas, it seems more likely that the velocity anomalies occur entirely within the crust.

Peak horizontal acceleration and velocity from strong-motion records including records from the 1979 imperial valley, California, earthquake

AbstractWe have taken advantage of the recent increase in strong-motion data at close distances to derive new attenuation relations for peak horizontal acceleration and velocity. This new analysis uses a magnitude-independent shape, based on geometrical spreading and anelastic attenuation, for the attenuation curve. An innovation in technique is introduced that decouples the determination of the distance dependence of the data from the magnitude dependence. The resulting equations arelog A = − 1.02 + 0.249 M − log r − 0.00255 r + 0.26 P r = ( d 2 + 7.3 2 ) 1 / 2 5.0 ≦ M ≦ 7.7 log V = − 0.67 + 0.489 M − log r − 0.00256 r + 0.17 S + 0.22 P r = ( d 2 + 4.0 2 ) 1 / 2 5.3 ≦ M ≦ 7.4where A is peak horizontal acceleration in g, V is peak horizontal velocity in cm/ sec, M is moment magnitude, d is the closest distance to the surface projection of the fault rupture in km, S takes on the value of zero at rock sites and one at soil sites, and P is zero for 50 percentile values and one for 84 percentile values.We considered a magnitude-dependent shape, but we find no basis for it in the data; we have adopted the magnitude-independent shape because it requires fewer parameters.

Spatial variation of crustal seismic velocities in southern California

abstractArrival-time data for local earthquakes were used to study lateral velocity variations and error statistics for southern California. Crustal P velocities averaged over the major geomorphic provinces vary by only a few per cent. Regions of relatively high velocity include the Peninsular ranges, the Imperial valley, the Pomona basin, and the Colorado desert. The Santa Monica, southern Sierra, San Bernardino, and San Jacinto mountains are relatively slow, as is the offshore area. Near-surface station delays, which are unknown to within several tenths of a second, are a major source of uncertainty in the regional velocities.Arrival-time errors include two types: (1) small errors caused by imperfect timing and unmodeled velocity variations; and (2) larger errors apparently caused by improper identification of arrivals and by blunders. We found no reliable way to identify the latter errors unless they result in large arrival-time residuals. For a strongly edited catalog, the variance of arrival-time residuals appears to increase linearly with epicentral distance, as predicted for wave propagation in a randomly heterogeneous medium. The variance of residuals is strongly station dependent. Residuals are nearly Gaussian within the 70 per cent confidence interval, but not outside this interval. The 95 per cent confidence limit occurs at about three standard deviations.

Asymptotic ray theory and synthetic seismograms for laterally varying structures: theory and application to the imperial valley, California

The interpretation of refraction profiles that traverse laterally varying velocity structures has been hindered by lack of a practical algorithm for computing synthetic seismograms to compare with observations. However, a modification of zero-order asymptotic ray theory to incorporate the amplitudes of rays that turn in a velocity gradient, as well as reflected waves, allows the computation of high-frequency synthetic seismograms for laterally varying velocity structures. The method is general in that synthetic seismograms may be computed for any structure through which rays can be traced. We have modeled seismic refraction data from the Imperial Valley, California, by applying this method. A major feature of our model is a sedimentary column that thickens from -4 km at the Salton Sea to -5.5 km at the United StatesMexico border. To approximate the observed amplitude behavior, a dipping velocity discontinuity was modeled near 13-km depth, but velocity gradients were found to be more appropriate than sharp boundaries in the rest of the model.

Potential air quality impacts of large-scale geothermal energy development in the Imperial Valley

This report is an assessment of the potential impact on air quality of large-scale (3000 MW) geothermal development in California's Imperial Valley. The assessment is based on the predictions of numerical atmospheric transport models. Emission rates derived from analyses of the composition of geothermal fluids in the region and meteorological data taken at six locations in the valley over a 1-y period were used as input to the models. Hydrogen sulfide is the emission of major concern. Our calculations predict that at the 3000-MW level (with no abatement), the California 1-h standard for H 2S (42 μg m −3) would be violated at least 1% of the time over an area of approximately 1500 km 2 (about 1 3 of the valley area). The calculations indicate that an H 2S emission rate below 0.8 g s −1 per 100-MW unit is needed to avoid violations of the standard beyond a distance of 1 km from the source. Emissions of ammonia, carbon dioxide, mercury, and radon are not expected to produce significant ground level concentrations, nor is the atmospheric conversion of hydrogen sulfide to sulfur dioxide expected to result in significant SO 2 levels.

WATER SUPPLY DILEMMAS OF GEOTHERMAL DEVELOPMENT IN THE IMPERIAL VALLEY OF CALIFORNIA1

Abstract: There are four known geothermal resource areas in the Imperial Valley that have a combined potential of over 4,000 megawatts of electrical energy for 25 years. Water resources available to support geothermal enerfy development are imprted Colorado River water, agricultural waste waters, Salton Sea water, and groundwater. In addtion, geothermal power plants can produce their own cooling water from steam condensate. Nevertheless, the relatively high water requirements of geothermal facilities along with a series of real and potential constraints may cause water supply dilemmas involving both the acquistion and use of cooling water. Important constraints are institutional policies, water supply costs, technical problems, and impacts upon the Salton Sea. These constranits and related dilemmas are examined in light of relevanty information on the valley's water resources, geothermal resources and energy technologies, cooling water requrements, and water supply options.

Source parameters for the January 1975 Brawley — Imperial valley earthquake swarm

Source parameters for the January 1975 Brawley — Imperial valley earthquake swarm

Salt and Water Balance in Imperial Valley, California

AbstractSalt balance (SB = Veff.w · Ceff.w − Vinf.w · Cinf.w) of the Imperial Valley (IV) has been determined annually since 1943 by the Imperial Irrigation District. Salinity trends in the valley are assessed from biweekly measurements of the volume, V, and concentration, C, of influent, inf.w, and effluent, eff.w, waters. In this paper we summarize the SB data, evaluate their significance, and suggest approaches for assessing salinity trends in the soils of the valley.The SB data reflected the cropping and water use patterns in the valley. However, the data were insufficient to distinguish origin of water and salt in effluent waters or to provide information about changes in root zone salinity. In 1973 total evapotranspiration (ET) by crops in the valley was estimated to be 229 × 103 ha‐m, equivalent to 70% of the water delivered to the farmers. Deductions as to Cl‐ composition of influent and effluent during 1973 suggest that the Cl‐ load in the effluent water was contributed as follows: 54.7% from ground water, 35.0% from root zone drainage water, and 10.3% from tail water (runoff).A more definitive interpretation of the salt balance data would require more accurate evaluation of volume of tail and consumptive use waters and volume and concentration of root zone percolate. If this information cannot be obtained on a valley‐wide basis, then an alternative approach is to establish a representative number of soil salinity monitoring plots through the valley and assess their root zone salinity periodically.

The application of the Na-K-Ca geothermometer to thermal areas of Utah and the imperial valley, California

The sodium (Na), potassium (K), calcium (Ca) geothermometer is discussed as a tool for locating and evaluating areas prospectively valuable for geothermal development. Presented is a regional analysis of the major thermal springs of Utah to demonstrate the use of the Na-K-Ca geothermometer as a rapid and meaningful method of geothermal reconnaissance. Of the thermal areas of Utah, Roosevelt Hot Springs show the greatest geothermal potential where estimated temperatures are nearly 300 °C. This compares favorably with estimated and measured temperatures from proven geothermal fields such as Cerro Prieto in Mexico and the Salton Sea field of California. Also presented are more detailed studies of LaVerkin Ho 1 Springs and Wilson Hot Springs, Utah, and the Mesa anomaly, Imperial Valley, California. These studies examine the accuracy and precision of the Na-K-Ca geothermometer and the physical conditions under which it can be reliably used to predict subsurface temperatures. It is shown that in the saline environment of the Imperial Valley, it should be possible to obtain useful information even though the results might normally be considered suspect due to concentration or dilution of the analyzed samples.

Geothermal resources in the imperial valley of california

The Imperial Valley is a major rift valley characterized by unusually high heat flow and large quantities of water in storage in the thick fill of alluvium provided by the sediments of the delta of the Colorado River. The inventory of hot water appears to be sufliciently large that if used for water desalination it might add several million acreleet of new water to the resources of the lower Colorado River basin. This distilled water would serve to lower river salinity and provide extra water to help meet the U. S. — Mexico treaty commitments. A major fraction of water desalination costs lie in the cost of energy and are related to desalination technology which is directly related to water chemistry. The discovery of low salinity geothermal waters in the Imperial Valley opened th possibility for a major breakthrough in lowered water desalination costs. We have tried to develop a broad understanding of the origins of the waters of the Imperial Valley and how natural recharge occurs. The chemical composition of the waters of the central portion of Imperial Valley basin waters, while not that of present surface flow of the rivers, nevertheless does have a close affinity to Colorado River water. No sea water seems to be present in the valley although marine sediments appear to occur on basement on West Mesa and on basement to the east in Arizona south of Yuma. Low salinity waters dominate the basin hydrology and waters as saline or more saline than sea water appear to be restricted to the immediate area of the Salton Sea. The isotope work of T. Coplen makes it possible to determine the relative contribution of precipitation runoff from California watersheds and from Colorado River water. Both sources are significant. The Colorado River water in aquifers from 100–400 m appears to have been entrapped from a relatively homogeneous basin which was subject to substantial evaporation. Its original source was snow melt water from the Colorado River. Five types of waters, none of them sea water, were recognized by their salt geochemistry. Bromide/chloride data are particularly effective in resolving different types of water masses. The bromide/chloride data agree with the isotope data and identify rainfall and precipitation runoff from the high mountains to the west. Modern Colorado River water is easily recognized by its salts and two types of ancient Colorado River waters from previous lake stage are proposed on the basis of the bromide/chloride data. One old lake occurring during the pluvial stage associated with the last Ice Age is proposed to account for much of the water in artesian aquifers. Another younger lake stage, possibly with Lake Cahuilla affinities is also suggested. Mountain runoff waters can be distinguished in the subsurface by their relatively lower salinity and high bicarbonate concentration, and their heavy isotopic composition. Revised fluid reserve calculations based on additional porosity data continue to show that the low salinity water resources of the Imperial Valley may exceed two billion acre-feet. The oceanic plate tectonic model is modified in the Imperial Valley by the evidence of a series of complex blocks with the generation of both tensional and compressional features in the valley. Major strike slip faults dominate the tectonic fabric but conjugate features increase complexity by a large degree and a major amount of work will be needed before any geologically sound structural models can be generated. Xenoliths within the obsidians at the volcanoes at the south end of the Salton Sea provide samples of the basement under the Imperial Valley. These xenoliths include partially remelted granitic rocks, fragments of basalt, greenschist, and baked shale and sandstone. This is taken as evidence that the basement in the valley consists in part of partially remelted granite. This would render basement plastic and readily deformed. The source of the heat is suggested to be derived from basalt that comes into the basement and deeper sediments from below. This upward movement of basalt along a spreading zone is the continental equivalent to a sea floor spreading area. In the continental case the insulating blanket of wet sediment retains the heat and appears to produce a major geothermal resource. The geothermal resources of the Imperial Valley are the aggregate of the thermal energy of the large inventory of subsurface water heated by the complex mix of intrusive phenomena. The net result is to generate a polygenetic geothermal resource of very large dimensions.

Application of electrical resistivity and gravimetry in deep geothermal exploration

The electrical resistivity method has been proven applicable to geothermal exploration because of the direct relationship between fluid and rock temperatures on the one hand electrical conductivity on the other. The problem of exploitation of a surface technique, such as resistivity, to the determination of geothermal gradients or ‘hot spots’ is complicated by the other geological parameters which affect resistivity: porosity, fluid salinity, cementation factor and clay content. However, by rational application of common geological techniques it is possible at times to isolate electrical resistivity changes due to temperature alone, and calculate the geothermal gradients. Nomograms are provided for calculation of some of the parameters which affect resistivity. Under some geologic conditions, gravimetry provides a useful clue as to the areas of abnormal heat flow, due to the metamorphism of sediments by circulating plumes of mineralized fluids. A case history of the application of the above methods to the geothermal exploration of the Imperial Valley graben of southern California is described showing how the above techniques were employed to detail the geothermal characteristics of portions of the valley.

The Early Development of California's Imperial Valley: Part II

Imperial Valley had reached a crucial point in its development by 1905. The irrigation developers of the valley had promoted colonization successfully and had been able to supply water needs of the valley in one way or another. The decision to initiate a new intake was reached only after thoughtful deliberation, but that decision resulted in a serious setback to the California Development Company: the inability of company engineers to close the intake and finish what they had begun resulted in severe floods within the valley, floods that caused considerable damage and remained unchecked for two years.1 The company placed responsibility for the disaster primarily on the engineers. Company officers felt the engineers had not adequately informed them of all the facts concerned in cutting the new canal. They claimed inferior materials were purchased and used, as well as second-rate construction procedures. The engineers, on the other hand, blamed inadequate funds to purchase reliable materials, and alleged personal gain had been the foremost motivation of company officials.

World rift system

The midocean ridge system is a continuous tectonic feature over 60,000 km in length which covers an area equal to that of all the continents (Figure 1). It is the longest single geological structure on the surface of the Earth.Associated with the center of the ridge over much of its length is a fracture or rift which is the locus for many shallow earthquakes. Although the ridge system is generally restricted to the ocean basins, it crosses the continental margins at several points. One point is off the west coast of Mexico, where it extends through the Gulf of Baja California and into the fracture zones of the western United States; another point, located in the Indian Ocean, extends through the Gulf of Aden into the Red Sea. Here it bifurcates, one branch extending north to the Gulfs of Suez and Aqaba, the Dead Sea, and the Jordan valley, the other branch extending south to the great east African rift‐valleys. Topographic profiles across the system (Figure 2) illustrate the changes occurring as one goes from continent to ocean. The Gulf of Aqaba is a narrow rift marked by negative Bouguer gravity anomalies which, like the Gulf of Suez, bears a close resemblance to the east African rifts. The rift zone is much wider in the Red Sea, and it is marked by positive Bouguer gravity anomalies and, in the southern part especially, by very strong magnetic anomalies in the central portion. Seismic refraction measurements indicate that the shelves of the Red Sea are founded upon downdropped continental crustal blocks (5.8 km/sec), whereas the axial trough is based on high‐velocity (7+ km/sec) basic material (Figure 3). Similar high velocities are found in the Gulf of Aden, where the soundings indicate a rift to the west grading into a low ridge with a median rift as one moves toward the Indian Ocean. In the Indian Ocean a true ocean ridge system is found with an axial rift marked by numerous earthquake epicenters and frequently by a distinctive magnetic anomaly. Although there are few seismic refraction measurements in the Indian Ocean, the structure must be similar to other parts of the ridge system where velocities of 7+ km/sec are found at relatively shallow depths. Heat flow measurements from the Atlantic, Pacific, and Indian oceans show systematically higher values in the vicinity of the ridge, although the amount of increase varies (Figures 4 and 5). Heat flow measurements in the marginal Gulf of Aden and in the Gulf of Lower California also reveal higher than normal values. Several wells drilled in the Imperial valley just north of the Gulf of Lower California have encountered bottom hole temperatures in excess of 550°C and an unusually high concentration of minerals in the brine. Of a few measurements made recently in Lake Nyasa, the most reliable indicated high values due to a fairly local heat source.

BARCHAN-DUNE MOVEMENT IN IMPERIAL VALLEY, CALIFORNIA

Research Article| February 01, 1964 BARCHAN-DUNE MOVEMENT IN IMPERIAL VALLEY, CALIFORNIA JOSEPH T LONG; JOSEPH T LONG TOPOGRAPHIC DIVISION, U. S. GEOLOGICAL SURVEY, MENLO PARK, CALIF.; CALIFORNIA INSTITUTE OF TECHNOLOGY, PASADENA, CALIF. Search for other works by this author on: GSW Google Scholar ROBERT P SHARP ROBERT P SHARP TOPOGRAPHIC DIVISION, U. S. GEOLOGICAL SURVEY, MENLO PARK, CALIF.; CALIFORNIA INSTITUTE OF TECHNOLOGY, PASADENA, CALIF. Search for other works by this author on: GSW Google Scholar GSA Bulletin (1964) 75 (2): 149–156. https://doi.org/10.1130/0016-7606(1964)75[149:BMIIVC]2.0.CO;2 Article history received: 12 Aug 1963 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JOSEPH T LONG, ROBERT P SHARP; BARCHAN-DUNE MOVEMENT IN IMPERIAL VALLEY, CALIFORNIA. GSA Bulletin 1964;; 75 (2): 149–156. doi: https://doi.org/10.1130/0016-7606(1964)75[149:BMIIVC]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The movement of 47 barchan dunes on the west side of Salton Sea, California, ranged from 325 to 925 feet over the 7 years between 1956 and 1963, an average of 82 feet per year. During the 15 years between 1941 and 1956, the movement of 34 of these dunes ranged between 350 and 1200 feet, an average of 50 feet per year. This difference in average movement during the two intervals is attributed primarily to increased sand supply. Movement (D) plotted against height of slip face (H) for the Salton dunes fits reasonably well with Finkel's reciprocal curve (1/D = n + k H) or with a law of the type D = PerH. Factors other than height affect the rate of movement, one of the more important being the state of the dune, whether growing or steady state. Barchan shape, whether fat or slim, may also influence the rate of movement of growing dunes. None of these dunes needs be more than 300 years old. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.