Imperial Valley Research Articles

Effectiveness of Lateral Load Resisting Systems for Open Ground+20 Storied RC Framed Structure

Abstract: In a highly populated country like India, problem of parking of the vehicles arises, this problem leaves no option for design of open ground storey buildings. Since there are no infill walls in ground storey, stiffness in the upper storey is much more than the ground storey. The columns in the ground storey are heavily stressed, therefore it is required that the ground storey columns must have sufficient strength and adequate ductility, the increased base shear is resisted entirely by the columns of ground storey only. These buildings are vulnerable due to the sudden lowering of stiffness and strength in the ground storey. This results in the attraction of more earthquake forces for the lower time periods, which also results in snapping of lateral ties in column, crushing of core concrete, buckling of longitudinal bars and finally shear failure in open ground storey columns due to lateral earthquake forces. Solution for this problem is to prevent the failure of open ground storey columns due to lateral earthquake forces by providing the lateral load resisting system. Many times, stiffness of walls is not considered while designing, this results in inaccurate designing of elements. An Open Ground +20 storied RC frame subjected to strong motion earthquakes viz. Duzce in Turkey (12/11/1999), Erzincan in Turkey (13/03/1992), Imperial valley at El-centro (19/05/1940), Landers (28/06/1992) and Nahanni in Canada (23/12/1985) creating soft storey effect at ground storey so it should be provided with lateral load resisting systems viz, Shear wall, steel bracing, lead rubber bearing base isolator with different configurations. Performance of equivalent diagonal strut provided to structure is compared with brick work modelled as actual brick work, equivalent diagonal struts, and considering only the mass of brick work. Time History Analysis is used in a RC framed building using ETABS Version18 and SAP2000 Version20 software in comparison with Response quantities Roof displacement, soft storey check, Base shear, overturning moment and storey drift. In this research, equivalent diagonal struts are provided as brick masonary, which shows accurate behavior of structure under strong ground motions as mass and stiffness both are considered during analysis. When Open ground storied structure is subjected to strong ground motions, stiffness at ground storey is drastically reduced. When structure is assigned with Lateral Load Resisting Systems, shear wall with configuration shear wall at ground storey and 1st storey, stiffness at ground storey is increased to 81% and 82% in X and Y direction respectively within permissible limits. Hence it can be concluded that when there is soft storey effect at open ground, structure becomes hazardous in presence of strong ground motions. When structure is subjected to strong ground motions, the vulnerability condition is high. Since we have performed non-linear dynamic time history analysis, more accurate results can be obtained as non-linear analysis considers vertical irregularities

Evaluating Irrigation Performance and Water Productivity Using EEFlux ET and NDVI

Southern California’s Imperial Valley (IV) faces serious water management concerns due to its semi-arid environment, water-intensive crops and limited water supply. Accurate and reliable irrigation system performance and water productivity information is required in order to assess and improve the current water management strategies. This study evaluates the spatially distributed irrigation equity, adequacy and crop water productivity (CWP) for two water-intensive crops, alfalfa and sugar beet, using remotely sensed data and a geographical information system for the 2018/2019 crop growing season. The actual crop evapotranspiration (ETa) was mapped in Google Earth Engine Evapotranspiration Flux, using the linear interpolation method in R version 4.0.2. The approx() function in the base R was used to produce daily ETa maps, and then totaled to compute the ETa for the whole season. The equity and adequacy were determined according to the ETa’s coefficient of variation (CV) and relative evapotranspiration (RET), respectively. The crop classification was performed using a machine learning approach (a random forest algorithm). The CWP was computed as a ratio of the crop yield to the crop water use, employing yield disaggregation to map the crop yield, using county-level production statistics data and normalized difference vegetation index (NDVI) images. The relative errors (RE) of the ETa compared to the reported literature values were 7–27% for alfalfa and 0–3% for sugar beet. The average ETa variation was low; however, the spatial variation within the fields showed that 35% had a variability greater than 10%. The RET was high, indicating adequate irrigation; 31.5% of the alfalfa and 12% of the sugar beet fields clustered in the Valley’s central corner were consuming more water than their potential visibly. The CWP showed wide variation, with CVs of 32.92% for alfalfa and 25.4% for sugar beet, signifying a substantial scope for CWP enhancement. The correlation between the CWP, ETa and yield showed that reducing the ETa to approximately 1500 mm for alfalfa and 1200 mm for sugar beet would help boost the CWP without decreasing the yield, which is nearly equivalent to 44.52M cu. m (36,000 acre-ft) of water. The study’s results could help water managers to identify poorly performing fields where water conservation and management could be focused.

Coherence-guided InSAR deformation analysis in the presence of ongoing land surface changes in the Imperial Valley, California

While the quality and availability of Interferometric Synthetic Aperture Radar (InSAR) data has dramatically improved in recent years, InSAR analysis and interpretation remain challenging in actively deforming regions with extensive agricultural activities, where vegetation changes and soil moisture variability can degrade data quality or introduce confounding signals. Here we use Sentinel-1 satellite imagery for the Imperial Valley, California, over the period of 2015–2019 to explore how factors specific to land surface changes may impact InSAR time series and to resolve time-varying deformation due to tectonic processes and geothermal energy production. We examine the temporal variability of data quality, via interferometric phase coherence, at high spatial resolution, taking into account the observation that some agricultural fields lie fallow for long time intervals punctuated by periods of cultivation. This strategy allows us to better distinguish signals and noise associated with agricultural activities, shoreline changes, or surface soil conditions. A series of masking, interpolation, and filtering steps facilitate phase unwrapping, and the unwrapped, unfiltered product is then recovered, reducing artifacts from spatial filtering. We adopt model-based tropospheric corrections to improve time series results, particularly in regions with high topographic relief, along with the use of distributed reference points to render a more uniform error structure. We validate InSAR observations with continuous GPS where available and find that the estimates of average line-of-sight (LOS) velocity over the valley from InSAR and GPS agree to ~3 mm/yr in areas with good data coverage. Discrepancies between the two estimates often exist in areas with lower InSAR data quality; in better-constrained areas, they appear to reveal signals attributable to surficial processes occurring in the uppermost soil layers. We observe a diverse suite of natural signals over multiple spatial scales, including steady interseismic deformation, seasonal lake-level-modulated signals at the southeastern Salton Sea shore, and transient slow slip on the Superstition Hills fault. In addition, we observe complex deformation at four geothermal fields within the valley. Extensive subsidence at the Salton Sea geothermal field suggests spatial overlap of anthropogenic and tectonic deformation, interspersed with potential surficial signals. Geothermal sites at East Mesa, North Brawley, and Heber exhibit smaller-amplitude, more localized deformation, often with nonlinear temporal trends. Our analysis demonstrates the need to assess whether InSAR signals result from surficial changes or deeper sources, and produces robust ground deformation data in support of efforts to study subsurface processes, manage geothermal operations, and improve hazard assessments.

Differential inflammatory potential of particulate matter (PM) size fractions from imperial valley, CA

Particulate matter (PM) in Imperial Valley originates from a variety of sources such as agriculture, traffic at the border crossing, emissions from the cross-border city of Mexicali, and the drying lakebed of the Salton Sea. Dust storms in Imperial Valley, California regularly lead to exceedances of the federal air quality standards for PM10 (diameter less than 10 μm). To determine if there are differences in the composition and biological response to Imperial County PM by size, ambient PM samples were collected from a sampling unit stationed in the northern-most part of the valley, South of the Salton Sea. Ultrafine, fine, and coarse PM samples were collected and extracted separately. Chemical composition of each size fraction was obtained after extraction by using several analytical techniques, and biological response was measured by exposing a cell line of macrophages to particles and quantifying subsequent gene expression. Biological measurements demonstrated coarse PM induced an inflammatory response in macrophages measured in increases of inflammatory markers IL-1ß, IL-6, IL-8 and CXCL2 expression, whereas ultrafine and fine PM only demonstrated significant increases in expression of CYP1a1. These differential responses were due not only to particle size, but to the distinct chemical profiles of each size faction as well. Community groups in Imperial Valley have already completed several projects to learn more about local air quality, giving residents access to data that provides real-time levels of PM2.5 and PM10 as well as recommendations on health-based practices dependent on the current AQI (air quality index). However, to date there is no information on the composition or toxicity of ambient PM from the region. The data presented here could provide more definitive information on the toxicity of PM by size, and further inform the community on local air quality.

Spatial Particulate Fields during High Winds in the Imperial Valley, California

We examined windblown dust within the Imperial Valley (CA) during strong springtime west-southwesterly (WSW) wind events. Analysis of routine agency meteorological and ambient particulate matter (PM) measurements identified 165 high WSW wind events between March and June 2013 to 2019. The PM concentrations over these days are higher at northern valley monitoring sites, with daily PM mass concentration of particles less than 10 micrometers aerodynamic diameter (PM10) at these sites commonly greater than 100 μg/m3 and reaching around 400 μg/m3, and daily PM mass concentration of particles less than 2.5 micrometers aerodynamic diameter (PM2.5) commonly greater than 20 μg/m3 and reaching around 60 μg/m3. A detailed analysis utilizing 1 km resolution multi-angle implementation of atmospheric correction (MAIAC) aerosol optical depth (AOD), Identifying Violations Affecting Neighborhoods (IVAN) low-cost PM2.5 measurements and 500 m resolution sediment supply fields alongside routine ground PM observations identified an area of high AOD/PM during WSW events spanning the northwestern valley encompassing the Brawley/Westmorland through the Niland area. This area shows up most clearly once the average PM10 at northern valley routine sites during WSW events exceeds 100 μg/m3. The area is consistent with high soil sediment supply in the northwestern valley and upwind desert, suggesting local sources are primarily responsible. On the basis of this study, MAIAC AOD appears able to identify localized high PM areas during windblown dust events provided the PM levels are high enough. The use of the IVAN data in this study illustrates how a citizen science effort to collect more spatially refined air quality concentration data can help pinpoint episodic pollution patterns and possible sources important for PM exposure and adverse health effects.

Seismic imaging of the metamorphism of young sediment into new crystalline crust in the actively rifting Imperial Valley, California

AbstractPlate‐boundary rifting between transform faults is opening the Imperial Valley of southern California and the rift is rapidly filling with sediment from the Colorado River. Three 65–90 km long seismic refraction profiles across and along the valley, acquired as part of the 2011 Salton Seismic Imaging Project, were analyzed to constrain upper crustal structure and the transition from sediment to underlying crystalline rock. Both first arrival travel‐time tomography and frequency‐domain full‐waveform inversion were applied to provide P‐wave velocity models down to ∼7 km depth. The valley margins are fault‐bounded, beyond which thinner sediment has been deposited on preexisting crystalline rocks. Within the central basin, seismic velocity increases continuously from ∼1.8 km/s sediment at the surface to >6 km/s crystalline rock with no sharp discontinuity. Borehole data show young sediment is progressively metamorphosed into crystalline rock. The seismic velocity gradient with depth decreases approximately at the 4 km/s contour, which coincides with changes in the porosity and density gradient in borehole core samples. This change occurs at ∼3 km depth in most of the valley, but at only ∼1.5 km depth in the Salton Sea geothermal field. We interpret progressive metamorphism caused by high heat flow to be creating new crystalline crust throughout the valley at a rate comparable to the ≥2 km/Myr sedimentation rate. The newly formed crystalline crust extends to at least 7–8 km depth, and it is shallower and faster where heat flow is higher. Most of the active seismicity occurs within this new crust.

Fault zone characteristics and basin complexity in the southern Salton Trough, California

Abstract Ongoing oblique slip at the Pacific–North America plate boundary in the Salton Trough produced the Imperial Valley (California, USA), a seismically active area with deformation distributed across a complex network of exposed and buried faults. To better understand the shallow crustal structure in this region and the connectivity of faults and seismicity lineaments, we used data primarily from the Salton Seismic Imaging Project to construct a three-dimensional P-wave velocity model down to 8 km depth and a velocity profile to 15 km depth, both at 1 km grid spacing. A VP = 5.65–5.85 km/s layer of possibly metamorphosed sediments within, and crystalline basement outside, the valley is locally as thick as 5 km, but is thickest and deepest in fault zones and near seismicity lineaments, suggesting a causative relationship between the low velocities and faulting. Both seismicity lineaments and surface faults control the structural architecture of the western part of the larger wedge-shaped basin, where two deep subbasins are located. We estimate basement depths, and show that high velocities at shallow depths and possible basement highs characterize the geothermal areas.

Born from a flood: The Salton Sea and its story of survival

The Salton Sea is a terminal lake located in the deepest point of the topographically closed Salton Trough in southeastern California. It is currently the largest lake in area in the state. It was created by a flooding event along the Colorado River in 1905–1907, similar to the way historical floods over past centuries created ephemeral incarnations of ancient Lake Cahuilla in the same location. Its position at the center of today’s Imperial Valley, a hot and arid locale home to some of the most productive irrigated agricultural lands in the United States, has ensured its ongoing survival through a delicate balance between agricultural runoff, its principal form of input, and vast evaporation losses. Nevertheless, its parallel role as a recreational resource and important wildlife habitat, established over its first century of existence, is threatened by increasing salinity decreasing water quality, and reduced water allocations from the Colorado River that feeds the valley’s agriculture. The Salton Sea faces an increasingly uncertain future that will be influenced by reduced water imports from the Colorado River, demands for additional water sources to support farming and energy industries in the valley, and needs to stabilize the lake salinity, maintain recreational resources, and preserve what have become important ecosystems and wildlife habitats.

Chasing Cheap Feedstocks

On the hot, dry agricultural land of California’s Imperial Valley, 17 new varieties of an unusual crop are being tested on a 100-acre plot. If the tests are successful, the valley’s bounty of lettu...

Work, struggle, death, and geographies of justice: The transformation of landscape in and beyond California's imperial valley

This paper examines the relation between labor, social struggle, and circulation (of capital and bodies) in the production of landscapes. Focusing on California's Imperial Valley and the stark relation there between living labor and dead laborers, and thus between the transformation of nature (the subject of labor) and systems of social reproduction, the paper examines the ways in which the real material conditions for justice—and injustice—are actively built into the ground.

IPM from Space: Using Satellite Imagery to Construct Regional Crop Maps for Studying Crop—Insect Interaction

Areawide knowledge of the population dynamics of a pest and its natural enemies is an integral part of regional integrated pest management (IPM) programs. Often, spatially explicit population modeling can provide a better understanding of large-scale population dynamics in relation to the crop system. A drawback of spatial modeling for studying insects in agricultural systems is that maps of the crop system used to drive the models often are complex and difficult to construct. Here, we show how regional crop systems can be mapped using satellite remote sensing imagery and how the resulting crop maps are prepared for use with spatially explicit models to study insect—crop interactions. As an example, we map the agricultural region in Imperial Valley, CA, where the whitefly Bemisia argentifolii Bellows & Perring is a serious pest. Landsat satellite images of the valley are combined with ground survey data on the crop system to construct whitefly resource maps. We use a maximum likelihood method and training data sets prepared from ground survey data to identify the multispectral signatures of crops and other land-cover features recorded by the Landsat sensors. Further, we use whitefly reproduction as an example to show how the classified crop maps can be transformed into maps of biological parameters. The parameter maps then can be used to drive a spatially explicit population model to study whitefly dynamics and management strategies in the crop system.

Subsurface drainage systems have little impact on water tables, salinity of clay soils

Subsurface drainage systems are traditionally installed in agricultural fields to control waterlogging (high water tables) and excess salinity affecting the crop root zone. However, in many clay fields of the Imperial Valley underlain by shallow fine-sand aquifers, the drains may be ineffective and provide limited relief for the root zone. After extensive work considering soil-water flow paths in a particular field at the UC Desert Research and Extension Center (DREC), we plugged whole-field drainage systems, then evaluated the impact on water-table levels and soil salinity during a 3-year period. We found that the shallow fine-sand aquifer underlying the DREC, originally identified in the 1950s, combined with the Imperial Irrigation District deep-ditch system, provided sufficient drainage relief for several areas of the DREC to successfully grow a variety of crops. Given the ineffectiveness of subsurface drainage systems in three different fields that had soil characteristics similar to more than half the Imperial Valley fields we expect that in many parts of the valley, augmentation of subsurface drainage systems through “splitting” the lateral drainline spacing may not be warranted. Indeed, efforts to reduce the salinity of heavier soils on the DREC, or elsewhere In the valley, may be better directed at improving water penetration and leaching of soils through deep ripping or other cultivation/mulching methods, rather than expending resources on improving the subsurface drainage system.

Salt Distributions in Cracking Soils and Salt Pickup by Runoff Waters

Detailed measurements were made of the levels and distributions of salts present in representative soil profiles and fields and associated tailwaters in the Imperial Valley of California. The findings showed that the potential salinity-pickup hazard may be greater in this valley that is dominated by cracking soils than classical theory would predict. Salts that would otherwise be “isolated” in seedbeds or leached downward during irrigations are more “exposed to” and “picked up by” the runoff water than previously recognized as a result of the flow of the irrigation water throughout the beds and horizontally in the topsoil via the extensive network of cracks and fractures that form in the cracking soils. As a result, the pattern of salinity within the beds of such soils is one-dimensional, rather than the expected, classical two-dimensional pattern. Salt content in the tailwater associated with cracking soils was higher and sustained over longer periods of time than in the case of noncracking soils.

Broadband modelling of regional seismograms: Imperial Valley to Pasadena

SUMMARY This paper addresses broadband wave propagation along a corridor from Imperial Valley to Pasadena, California. The path consists of 50 km of slow basin structure with a shallow Moho followed by 250 km of relatively normal southern California structure approaching Pasadena. Events occurring in the valley produce extended body wave codas which carry a dispersive waveform imprint along with longer period Rayleigh waves. Many features of these seismograms at periods greater than a few seconds can be modelled by applying a finite-difference technique to a 2-D structure. Shorter periods display complex behaviours not easily modelled by present techniques, especially for shallow events. Events occurring in the normal structure produce broadband SH-waveforms that can be modelled, analytically, if some extra empirically derived alignment parameters determined from calibration events are used. These parameters are determined by adjusting traveltime differentials between the decomposed wavefield S, sS, etc. For example, delays in sS relative to S correspond to local corrections for sediment cover for a particular source region. Source complexity such as asperities and directivity become increasingly important at shorter periods, as demonstrated by numerical experiments and observation.

Global positioning system measurements of strain accumulation across the Imperial Valley, California: 1986–1989

Global Positioning System (GPS) data collected in southern California from 1986 to 1989 indicate considerable strain accumulation across the Imperial Valley. Displacements are computed at 29 stations in and near the valley from 1986 to 1988, and at 11 sites from 1988 to 1989. The earlier measurements indicate 5.9 ±1.0 cm/yr right‐lateral differential velocity across the valley, although the data are heavily influenced by the 1987 Superstition Hills earthquake sequence. The 1988–1989 GPS displacements are best modeled by 5.0±0.9 cm/yr of valley crossing deformation, but rates calculated from 15 years of terrestrial geodetic measurements (3.7 ± 0.1 cm/yr) fit the data nearly as weh1. The relatively high GPS rates are suspect because some measurements, especially the east‐trending displacements, have large errors. There is evidence from GPS and very long baseline interferometry observations that the present strain rate along the southern San Andreas fault is smaller than the long‐term geologic estimate, suggesting a lower earthquake potential than is currently assumed. Correspondingly, a higher earthquake potential is suggested for the San Jacinto fault.

Enhanced pyrethroid hydrolysis in pyrethroid-resistant larvae of the tobacco budworm, Heliothis virescens (F.)

Larvae of Heliothis virescens (F.) collected from the field in the Imperial Valley of California were reared in the laboratory and selected periodically with flucythrinate. At the end of the selection experiment, this Imperial Valley (IV) strain had LD 50 values that were ca. 68, 53, 16, 23, and 2 times higher for flucythrinate, fenvalerate, DDT, carbaryl, and ethyl parathion, than a susceptible American Cyanamid laboratory strain (ACCO). This IV strain was then transferred to LSU, without further selection pressure, where it was found to be ca. 12.2-, 5.4-, and 2.5-fold less susceptible to trans-permethrin, cis-permethrin, and fenvalerate, respectively, when compared with another laboratory strain (LSU lab). Piperonyl butoxide did not synergize trans-permethrin in the IV strain. Conversely, profenofos increased the toxicity of trans-permethrin to levels nearly identical to that for the LSU lab strain. The rates of hydrolysis were ca. 2- to 3-fold higher in the IV strain than in the LSU lab strain for all three pyrethroids. Isoelectric focusing also indicated higher levels of trans-permethrin hydrolytic activity in the IV strain as opposed to the LSU lab strain as well as the presence of an additional peak of activity. These observations suggest that there is both a qualitative and a quantitative difference in the ability of the pyrethroid-resistant IV strain to hydrolyze pyrethroids.

Population dynamics and control strategy for Bemisia tabaci in the imperial valley, California

Bemisia tabaci (Gennadius) populations were monitored in 1983 in the Imperial Valley of California on cotton and alfalfa utilizing yellow sticky traps and leaf samples. The influence of B. tabaci populations on cotton and early defoliation of cotton on autumn-planted crops was discussed. Infrared aerial photography was used as a survey tool to locate high whitefly densities in cotton. Insecticide resistance, adverse effects of pesticides on beneficial arthropods and different developmental rates on cultivated crops were factors that enhanced B. tabaci population increases.

Inferred displacements, velocities and rotations of a long rigid foundation located at el centro differential array site during the 1979 imperial valley, california, earthquake

AbstractDigitally recorded acceleration time histories of the 1979 Imperial Valley earthquake by the five elements of the El Centro Differential Array are used to estimate the induced torsional and rocking vibrations of long structures in the near field of strong earthquakes. The underlying assumptions in these estimates are high rigidity of the foundation relative to the surrounding soil and its negligible mass. Based on these analyses, the peak rotation amplitude of an 18 m long foundation within 5 km of the fault is approximately 1 × 10−3 rad, or nearly 0·06 degrees, and decreases rapidly for larger foundation dimensions for either the rocking or torsional mode. The strongest impulses of rotations coincide with arrival of the S phase. This paper examines the sensitivity of the resulting peak displacement and particle velocity amplitudes to the foundation dimension. It is inferred that the base averaging effects of displacement and velocity fields at frequencies contributing to peak values (f < 1 Hz) are negligibly small. Rocking and torsional amplitudes for the specific site and geometry considered here show a tendency to reduce with the increase of foundation dimensions.

A comparative study of imperial valley (1979) main shock and first aftershock recordings as evidence of ground motion level dependent non‐linearities

A comparative study of imperial valley (1979) main shock and first aftershock recordings as evidence of ground motion level dependent non‐linearities

Two observations about low-frequency signals on accelerograms from the october 15, 1979 imperial valley, california earthquake

Accelerograms from the Imperial Valley have been integrated and baseline corrected by a simple procedure which keeps track of the signal that is removed at long periods. Specifically, acceleration is integrated once to obtain velocity, a linear baseline is subtracted from velocity, the velocity is integrated to displacement, and low order terms of a trigonometric expansion of displacement are subtracted. It is observed that even though this procedure is not suitable for routine processing, one obtains displacement traces which usually resemble the results obtained by standar methods. It is also observed that amplitudes of the trigonometric series expansions are consistent with a simple earthquake source theory for frequencies greater than 1/12 Hz, suggesting that the records are dominated by signal at those frequencies.