In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors. Common types of potential energy include the gravitational potential energy of an object that depends on its mass and its distance from the center of mass of another object, the elastic potential energy of an extended spring, the electric potential energy of an electric charge in an electric field; the unit for energy in the International System of Units is the joule, which has the symbol J. The term potential energy was introduced by the 19th-century Scottish engineer and physicist William Rankine, although it has links to Greek philosopher Aristotle's concept of potentiality. Potential energy is associated with forces that act on a body in a way that the total work done by these forces on the body depends only on the initial and final positions of the body in space; these forces, that are called conservative forces, can be represented at every point in space by vectors expressed as gradients of a certain scalar function called potential.
Since the work of potential forces acting on a body that moves from a start to an end position is determined only by these two positions, does not depend on the trajectory of the body, there is a function known as potential that can be evaluated at the two positions to determine this work. There are various types of potential energy, each associated with a particular type of force. For example, the work of an elastic force is called elastic potential energy. Chemical potential energy, such as the energy stored in fossil fuels, is the work of the Coulomb force during rearrangement of mutual positions of electrons and nuclei in atoms and molecules. Thermal energy has two components: the kinetic energy of random motions of particles and the potential energy of their mutual positions. Forces derivable from a potential are called conservative forces; the work done by a conservative force is W = − Δ U where Δ U is the change in the potential energy associated with the force. The negative sign provides the convention that work done against a force field increases potential energy, while work done by the force field decreases potential energy.
Common notations for potential energy are PE, U, V, Ep. Potential energy is the energy by virtue of an object's position relative to other objects. Potential energy is associated with restoring forces such as a spring or the force of gravity; the action of stretching a spring or lifting a mass is performed by an external force that works against the force field of the potential. This work is stored in the force field, said to be stored as potential energy. If the external force is removed the force field acts on the body to perform the work as it moves the body back to the initial position, reducing the stretch of the spring or causing a body to fall. Consider a ball whose mass is m and whose height is h; the acceleration g of free fall is constant, so the weight force of the ball mg is constant. Force × displacement gives the work done, equal to the gravitational potential energy, thus U g = m g h The more formal definition is that potential energy is the energy difference between the energy of an object in a given position and its energy at a reference position.
Potential energy is linked with forces. If the work done by a force on a body that moves from A to B does not depend on the path between these points the work of this force measured from A assigns a scalar value to every other point in space and defines a scalar potential field. In this case, the force can be defined as the negative of the vector gradient of the potential field. If the work for an applied force is independent of the path the work done by the force is evaluated at the start and end of the trajectory of the point of application; this means that there is a function U, called a "potential," that can be evaluated at the two points xA and xB to obtain the work over any trajectory between these two points. It is tradition to define this function with a negative sign so that positive work is a reduction in the potential, W = ∫ C F ⋅ d x = U − U where C is the trajectory taken from A to B; because the work done is independent of the path taken this expression is true for any trajectory, C, from A to B.
The function U is called the potential energy associated with the applied force. Examples of forces that have potential energies are spring forces. In this section the relationship between work and potential energy is presented in more detail; the line integral that defines work along curve C takes a special form if the force F is related to a scalar field φ so that F = ∇ φ = ( ∂ φ ∂ x, ∂
Concrete Portland cement concrete, is a composite material composed of fine and coarse aggregate bonded together with a fluid cement that hardens over time—most a lime-based cement binder, such as Portland cement, but sometimes with other hydraulic cements, such as a calcium aluminate cement. It is distinguished from other, non-cementitious types of concrete all binding some form of aggregate together, including asphalt concrete with a bitumen binder, used for road surfaces, polymer concretes that use polymers as a binder; when aggregate is mixed together with dry Portland cement and water, the mixture forms a fluid slurry, poured and molded into shape. The cement reacts chemically with the water and other ingredients to form a hard matrix that binds the materials together into a durable stone-like material that has many uses. Additives are included in the mixture to improve the physical properties of the wet mix or the finished material. Most concrete is poured with reinforcing materials embedded to provide tensile strength, yielding reinforced concrete.
Famous concrete structures include the Panama Canal and the Roman Pantheon. The earliest large-scale users of concrete technology were the ancient Romans, concrete was used in the Roman Empire; the Colosseum in Rome was built of concrete, the concrete dome of the Pantheon is the world's largest unreinforced concrete dome. Today, large concrete structures are made with reinforced concrete. After the Roman Empire collapsed, use of concrete became rare until the technology was redeveloped in the mid-18th century. Worldwide, concrete has overtaken steel in tonnage of material used; the word concrete comes from the Latin word "concretus", the perfect passive participle of "concrescere", from "con-" and "crescere". Small-scale production of concrete-like materials was pioneered by the Nabatean traders who occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan from the 4th century BC, they discovered the advantages of hydraulic lime, with some self-cementing properties, by 700 BC.
They built kilns to supply mortar for the construction of rubble-wall houses, concrete floors, underground waterproof cisterns. They kept the cisterns secret; some of these structures survive to this day. In the Ancient Egyptian and Roman eras, builders discovered that adding volcanic ash to the mix allowed it to set underwater. German archaeologist Heinrich Schliemann found concrete floors, which were made of lime and pebbles, in the royal palace of Tiryns, which dates to 1400–1200 BC. Lime mortars were used in Greece and Cyprus in 800 BC; the Assyrian Jerwan Aqueduct made use of waterproof concrete. Concrete was used for construction in many ancient structures; the Romans used concrete extensively from 300 BC to a span of more than seven hundred years. During the Roman Empire, Roman concrete was made from quicklime, pozzolana and an aggregate of pumice, its widespread use in many Roman structures, a key event in the history of architecture termed the Roman Architectural Revolution, freed Roman construction from the restrictions of stone and brick materials.
It enabled revolutionary new designs in terms of both structural dimension. Concrete, as the Romans knew it, was a revolutionary material. Laid in the shape of arches and domes, it hardened into a rigid mass, free from many of the internal thrusts and strains that troubled the builders of similar structures in stone or brick. Modern tests show that opus caementicium had as much compressive strength as modern Portland-cement concrete. However, due to the absence of reinforcement, its tensile strength was far lower than modern reinforced concrete, its mode of application was different: Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice consisted of rubble. Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.
The long-term durability of Roman concrete structures has been found to be due to its use of pyroclastic rock and ash, whereby crystallization of strätlingite and the coalescence of calcium–aluminum-silicate–hydrate cementing binder helped give the concrete a greater degree of fracture resistance in seismically active environments. Roman concrete is more resistant to erosion by seawater than modern concrete; the widespread use of concrete in many Roman structures ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example. Many Roman aqueducts and bridges, such as the magnificent Pont du Gard in southern France, have masonry cladding on a concrete core, as does the dome of the Pantheon. After the Roman Empire, the use of burned lime and pozzolana was reduced until the technique was all but forgotten between 500 and the 14th century. From the 14th century to the mid-18th century, the use of cement returned; the Canal du Midi was built using concrete in 1670.
The greatest step forward in the modern use
Castaic Lake is a reservoir formed by Castaic Dam on Castaic Creek, in the Sierra Pelona Mountains of northwestern Los Angeles County, United States, near the town of Castaic. The California Office of Environmental Health Hazard Assessment has issued a safe advisory for any fish caught in Castaic Lake and Castaic Lagoon due to elevated levels of mercury and PCBs; the 320,000 acre⋅ft lake, with a surface elevation of 1,500 feet above sea level, is the terminus of the West Branch California Aqueduct, though some comes from the 154 square miles Castaic Creek watershed above the dam. Castaic Lake is bisected by the Elderberry Forebay Dam, which creates the adjacent Elderberry Forebay; the aqueduct water comes from Pyramid Lake through the Angeles Tunnel and is used to power Castaic Power Plant, a pumped-storage hydroelectric facility on the northern end of the forebay. Water is powering the turbines, rather than being pumped by them. Castaic Lake is part of the Castaic Lake State Recreation Area.
Primary access is via Interstate 5 at exits 176B at the town of Castaic. Water from the lake is distributed throughout the northern portion of the Greater Los Angeles Area; some water is released into Castaic Lagoon below the dam, to maintain its water level for recreation. Castic Lagoon drains into Castaic Creek, which flows south until it meets the Santa Clara River, a few miles west of Santa Clarita. Castaic Lake has a lower lagoon with a swim beach, open from Memorial Day weekend to Labor Day weekend annually; this lake offers bass fishing in the upper and lower lake year-round and float tube fishing in the lower lake. Castaic Lake was one of the main filming locations for the Mighty Morphin Power Rangers series. Many of the action scenes were recorded here. Castaic Lake was the starting point for The Amazing Race 26 on November 12, 2014. NBC's Fear Factor was shot there. List of dams and reservoirs in California List of lakes in California List of largest reservoirs of California "Dams Within the Jurisdiction of the State of California".
California Department of Water Resources, Division of Safety of Dams. Archived from the original on 2012-03-09. Retrieved December 3, 2012. Castaic Lake State Recreation Area "California Public Utilities Commission"
California State Water Project
The California State Water Project known as the SWP, is a state water management project in the U. S. state of California under the supervision of the California Department of Water Resources. The SWP is one of the largest public water and power utilities in the world, providing drinking water for more than 23 million people and generating an average of 6,500 GWh of hydroelectricity annually. However, as it is the largest single consumer of power in the state itself, it has a net usage of 5,100 GWh; the SWP collects water from rivers in Northern California and redistributes it to the water-scarce but populous south through a network of aqueducts, pumping stations and power plants. About 70% of the water provided by the project is used for urban areas and industry in Southern California and the San Francisco Bay Area, 30% is used for irrigation in the Central Valley. To reach Southern California, the water must be pumped 2,882 feet over the Tehachapi Mountains, with 1,926 feet at the Edmonston Pumping Plant alone, the highest single water lift in the world.
The SWP shares many facilities with the federal Central Valley Project, which serves agricultural users. Water can be interchanged between SWP and CVP canals as needed to meet peak requirements for project constituents; the SWP provides estimated annual benefits of $400 billion to California's economy. Since its inception in 1960, the SWP has required the construction of 21 dams and more than 700 miles of canals and tunnels, although these constitute only a fraction of the facilities proposed; as a result, the project has only delivered an average of 2.4 million acre feet annually, as compared to total entitlements of 4.23 million acre feet. Environmental concerns caused by the dry-season removal of water from the Sacramento–San Joaquin River Delta, a sensitive estuary region, have led to further reductions in water delivery. Work continues today to expand the SWP's water delivery capacity while finding solutions for the environmental impacts of water diversion; the original purpose of the project was to provide water for arid Southern California, whose local water resources and share of the Colorado River were insufficient to sustain the region's growth.
The SWP was rooted in two proposals. The United Western Investigation of 1951, a study by the U. S. Bureau of Reclamation, assessed the feasibility of interbasin water transfers in the Western United States. In California, this plan contemplated the construction of dams on rivers draining to California's North Coast – the wild and undammed Klamath, Eel and Smith River systems – and tunnels to carry the impounded water to the Sacramento River system, where it could be diverted southwards. In the same year, State Engineer A. D. Edmonston proposed the Feather River Project, which proposed the damming of the Feather River, a tributary of the Sacramento River, for the same purpose; the Feather River was much more accessible than the North Coast rivers, but did not have nearly as much water. Under both of the plans, a series of canals and pumps would carry the water south through the Central Valley to the foot of the Tehachapi Mountains, where it would pass through the Tehachapi Tunnel to reach Southern California.
Calls for a comprehensive statewide water management system led to the creation of the California Department of Water Resources in 1956. The following year, the preliminary studies were compiled into the extensive California Water Plan, or Bulletin No. 3. The project was intended for "the control, conservation and utilization of the waters of California, to meet present and future needs for all beneficial uses and purposes in all areas of the state to the maximum feasible extent." California governor Pat Brown would say it was to "correct an accident of people and geography". The diversion of the North Coast rivers was abandoned in the plan's early stages after strong opposition from locals and concerns about the potential impact on the salmon in North Coast rivers; the California Water Plan would have to go ahead with the development of the Feather River alone, as proposed by Edmonston. The Burns-Porter Act of 1959 provided $1.75 billion of initial funding through a bond measure. Construction on Stage I of the project, which would deliver the first 2.23 million acre feet of water, began in 1960.
Northern Californians opposed the measure as a boondoggle and an attempt to steal their water resources. In fact, the city of Los Angeles –, to be one of the principal beneficiaries – opposed the project. Historians attribute the success of the Burns-Porter Act and the State Water Project to major agribusiness lobbying by J. G. Boswell II of the J. G. Boswell cotton company; the bond was passed on an narrow margin of 174,000 out of 5.8 million ballots cast. In 1961, ground was broken on Oroville Dam, in 1963, work began on the California Aqueduct and San Luis Reservoir; the first deliveries to the Bay Area were made in 1962, water reached the San Joaquin Valley by 1968. Due to concerns over the fault-ridden geography of the Tehachapi Mountains, the tunnel plan was scrapped. In 1973, the pumps and the East and West branches of the aqueduct were completed, the first water was delivered to Southern California. A Peripheral Canal, which would have carried SWP water around the vulnerable and ecologically sensitive Sacramento–San Joaquin River Delta, was rejected in 1982 due to environm
Hydroelectricity is electricity produced from hydropower. In 2015, hydropower generated 16.6% of the world's total electricity and 70% of all renewable electricity, was expected to increase about 3.1% each year for the next 25 years. Hydropower is produced in 150 countries, with the Asia-Pacific region generating 33 percent of global hydropower in 2013. China is the largest hydroelectricity producer, with 920 TWh of production in 2013, representing 16.9 percent of domestic electricity use. The cost of hydroelectricity is low, making it a competitive source of renewable electricity; the hydro station consumes no water, unlike gas plants. The average cost of electricity from a hydro station larger than 10 megawatts is 3 to 5 U. S. cents per kilowatt hour. With a dam and reservoir it is a flexible source of electricity since the amount produced by the station can be varied up or down rapidly to adapt to changing energy demands. Once a hydroelectric complex is constructed, the project produces no direct waste, in many cases, has a lower output level of greenhouse gases than fossil fuel powered energy plants.
Hydropower has been used since ancient times to perform other tasks. In the mid-1770s, French engineer Bernard Forest de Bélidor published Architecture Hydraulique which described vertical- and horizontal-axis hydraulic machines. By the late 19th century, the electrical generator was developed and could now be coupled with hydraulics; the growing demand for the Industrial Revolution would drive development as well. In 1878 the world's first hydroelectric power scheme was developed at Cragside in Northumberland, England by William Armstrong, it was used to power a single arc lamp in his art gallery. The old Schoelkopf Power Station No. 1 near Niagara Falls in the U. S. side began to produce electricity in 1881. The first Edison hydroelectric power station, the Vulcan Street Plant, began operating September 30, 1882, in Appleton, with an output of about 12.5 kilowatts. By 1886 there were 45 hydroelectric power stations in the U. S. and Canada. By 1889 there were 200 in the U. S. alone. At the beginning of the 20th century, many small hydroelectric power stations were being constructed by commercial companies in mountains near metropolitan areas.
Grenoble, France held the International Exhibition of Hydropower and Tourism with over one million visitors. By 1920 as 40% of the power produced in the United States was hydroelectric, the Federal Power Act was enacted into law; the Act created the Federal Power Commission to regulate hydroelectric power stations on federal land and water. As the power stations became larger, their associated dams developed additional purposes to include flood control and navigation. Federal funding became necessary for large-scale development and federally owned corporations, such as the Tennessee Valley Authority and the Bonneville Power Administration were created. Additionally, the Bureau of Reclamation which had begun a series of western U. S. irrigation projects in the early 20th century was now constructing large hydroelectric projects such as the 1928 Hoover Dam. The U. S. Army Corps of Engineers was involved in hydroelectric development, completing the Bonneville Dam in 1937 and being recognized by the Flood Control Act of 1936 as the premier federal flood control agency.
Hydroelectric power stations continued to become larger throughout the 20th century. Hydropower was referred to as white coal for its plenty. Hoover Dam's initial 1,345 MW power station was the world's largest hydroelectric power station in 1936; the Itaipu Dam opened in 1984 in South America as the largest, producing 14,000 MW but was surpassed in 2008 by the Three Gorges Dam in China at 22,500 MW. Hydroelectricity would supply some countries, including Norway, Democratic Republic of the Congo and Brazil, with over 85% of their electricity; the United States has over 2,000 hydroelectric power stations that supply 6.4% of its total electrical production output, 49% of its renewable electricity. The technical potential for hydropower development around the world is much greater than the actual production: the percent of potential hydropower capacity that has not been developed is 71% in Europe, 75% in North America, 79% in South America, 95% in Africa, 95% in the Middle East, 82% in Asia-Pacific.
The political realities of new reservoirs in western countries, economic limitations in the third world and the lack of a transmission system in undeveloped areas result in the possibility of developing 25% of the remaining technically exploitable potential before 2050, with the bulk of that being in the Asia-Pacific area. Some countries have developed their hydropower potential and have little room for growth: Switzerland produces 88% of its potential and Mexico 80%. Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator; the power extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the head. A large pipe delivers water from the reservoir to the turbine; this method produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, the excess generation capacity is used to pump water into the higher reservoir.
When the demand becomes greater, water is released back into the lower reservoir through a turbine. Pumped-storage schemes provide the most commercially important means of large-scale grid energy storage and improve the daily capacity factor of the generation system. Pumped storag
San Luis Reservoir
The San Luis Reservoir is an artificial lake on San Luis Creek in the eastern slopes of the Diablo Range of Merced County, California 12 mi west of Los Banos on State Route 152, which crosses Pacheco Pass and runs along its north shore. It is the fifth largest reservoir in California; the reservoir stores water taken from the San Joaquin-Sacramento River Delta. Water is pumped uphill into the reservoir from the O'Neill Forebay, fed by the California Aqueduct and is released back into the forebay to continue downstream along the aqueduct as needed for farm irrigation and other uses. Depending on water levels, the reservoir is nine miles long from north to south at its longest point, five miles wide. At the eastern end of the reservoir is the San Luis Dam, or the B. F. Sisk Dam, the fourth largest embankment dam in the United States, which allows for a total capacity of 2,041,000 acre feet. Completed in 1967 on land part of Rancho San Luis Gonzaga, the 12,700 acres reservoir is a joint use facility, being a part of both the California State Water Project and Central Valley Project, which together form a network of reservoirs, pumping stations, 550 miles of canals and major conduits to move water across California.
The San Luis Reservoir is located in Merced County, has a visitor center located at the Romero Outlook where visitors can learn more about the dam and reservoir. The surface of the reservoir lies at an elevation of 544 ft, with the O'Neill Forebay below the dam at 225 ft above sea level; this elevation difference allows for a hydroelectric plant to be constructed - the Gianelli Hydroelectric Plant. Power from this plant is sent to Los Banos via a short power line; those 500 kV wires, carrying both the power generated here and elsewhere, leave the area and cross the O'Neill Forebay on several man-made islands. San Luis Reservoir supplies water to 63,500 acres of land in the Santa Clara Valley west of the Coast Ranges. San Justo Dam stores water diverted from San Luis Reservoir through the Pacheco Tunnel and Hollister Conduit, which travel through the Diablo Range. A separate canal, the Santa Clara Tunnel and Conduit, carries water to the Coyote Pumping Station in the Santa Clara Valley. San Luis Reservoir is part of the larger San Luis Reservoir State Recreation Area and therefore offers many recreational opportunities for fishermen and campers.
The park is patrolled by California State Park Peace Officers by vehicle and off-highway vehicle. In addition to camping and boating, day use picnic areas are available at San Luis Creek, an off-highway vehicle area is available east of the main area at the intersection of Gonzaga Road and Jaspar-Sears Road. Camping is available at four campgrounds; the Basalt Campground on the south-eastern edge of the lake with 79 developed family campsites. Water faucets are available nearby, some sites can handle RV's to a length of 40 feet. San Luis Creek Campground on O'Neill Forebay with 53 sites with water and electric hook-ups. Medeiros Campground has primitive campsites along the southern shoreline of O'Neill Forebay; this campground has drinking water at chemical toilets. Los Banos Creek Campground has limited turn-around space, it is not suitable for trailers or motor homes. Drinking water and chemical toilets are available. Improved boat launch ramps are offered at the Basalt area. Due to the reservoir's water being imported from the Sacramento River Delta, San Luis shares many of its fish species with that area, including largemouth bass, striped bass, bluegill, yellow perch, occasional sturgeon and salmon.
The California Office of Environmental Health Hazard Assessment has developed a safe eating advisory for fish caught in the San Luis Reservoir based on levels of mercury or PCBs found in local species. The lake is noted for its high winds and has wind warning lights at Romero Outlook, Basalt Campground, Quien Sabe Point; the National Weather Service has maintained a cooperative weather station at San Luis Dam since 1963. Based on those records, average January temperatures are a maximum of 54.3 °F and a minimum of 37.9 °F and average July temperatures are a maximum of 92 °F and a minimum of 64.0 °F. There are an average of 69.3 days with highs of 90 °F or higher and an average of 14.1 days with lows of 32 °F or lower. The record high temperature was 110 °F on July 24, 2006, the record low temperature was 14 °F on December 22, 1990. Average annual precipitation is 10.36 in. There are an average of 57 days annually with measurable precipitation; the wettest year was 1998 with 25.06 in and the driest year was 1989 with 4.88 in.
The most precipitation in one month was 9.03 in in February 1998. The most precipitation in 24 hours was 3.70 in on May 6, 1998. Snow falls at the reservoir, but 1.2 in of snow fell on January 9, 2001. List of dams and reservoirs in California List of lakes in California List of largest reservoirs in the United States List of largest reservoirs of California Department of Water Resources. "Station Meta Data: San Luis Reservoir ". California Data Exchange Center. State of California. Retrieved 2009-04-01. Allan, Stuart. California Road and Recreation Atlas. Medford, OR: Benchmark Maps. p. 75. ISBN 0-929591-80-1. California State Parks The Center for Land Use Interpretation California Dept of Water Resources Daily Reservoir Storage Summary
Kern County, California
Kern County is a county in the U. S. state of California. As of the 2010 census, the population was 839,631, its county seat is Bakersfield. Kern County comprises California Metropolitan statistical area; the county spans the southern end of the Central Valley. Covering 8,161.42 square miles, it ranges west to the southern slope of the Coast Ranges, east beyond the southern slope of the eastern Sierra Nevada into the Mojave Desert, at the city of Ridgecrest. Its northernmost city is Delano and its southern reach expands just beyond Lebec to Grapevine and the northern tip of the parallel Antelope Valley; the county's economy is linked to agriculture and to petroleum extraction. There is a strong aviation and military presence, such as Edwards Air Force Base, the China Lake Naval Air Weapons Station, the Mojave Air and Space Port, it is one of the fastest-growing areas in the United States in terms of population growth, but suffers from significant water supply issues and poor air quality. The area was claimed by the Spanish in 1769.
In 1772 Commander Don Pedro Fages became the first European to enter it, from the south by way of the Grapevine Canyon. Kern County was the site of the Battle of San Emigdio, in March 1824, between the Chumash Indians of Mission Santa Barbara who rebelled against the Mexican government's taking over mission property and ejecting the natives; this battle with Mexican forces from Monterey under the command of Carlos Carrillo took place at the canyon where San Emigdio Creek flows down San Emigdio Mountain and the Blue Ridge south of Bakersfield near today's Highway 166. It was a low-casualty encounter, with only four Indians killed, no Mexicans. In the beginning, the area that became Kern County was dominated by mining in the mountains and in the desert. In 1855 an attempt to form a county in the area was made when the California legislature took the southeastern territory of Tulare County on the west of the Sierra Nevada Mountains for Buena Vista County, but it was never organized prior to 1859, when the enabling legislation expired.
The south of Tulare County was organized as Kern County in 1866, with additions from Los Angeles and San Bernardino Counties. Its first county seat was in the mining town of Havilah, in the mountains between Bakersfield and Tehachapi; the flatlands were considered inhospitable and impassable at the time due to swamps, tule reeds and diseases such as malaria. This changed when settlers started draining lands for farming and constructing canals, most dug by hand by hired Chinese laborers. Within 10 years the valley surpassed the mining areas as the economic center of the county, the county seat was moved as a result from Havilah to Bakersfield in 1874; the discovery well of the Kern River Oil Field was dug by hand in 1899. Soon the towns of Oil City, Oil Center and Oildale came into existence; the county derives its name from the Kern River, named for Edward Kern, cartographer for General John C. Frémont's 1845 expedition; the Kern River was named Rio Bravo de San Felipe by Father Francisco Garcés when he explored the area in 1776.
Severe earthquakes have struck Kern County within historical times, including the 1857 Fort Tejon earthquake. On July 21, 1952, an earthquake occurred with the epicenter about 23 miles south of Bakersfield, it killed 12 people. In addition to the deaths, it was responsible for hundreds of injuries and more than $60 million in property damage; the main shock was felt over much of California and as far away as Phoenix and Reno, Nevada. The earthquake occurred on the White Wolf Fault and was the strongest to occur in California since the 1906 San Francisco earthquake. Tehachapi suffered the greatest damage and loss of life from the earthquake, though its effects were felt throughout central and southern California; the event had a significant aftershock sequence that persisted into July and August with the strongest coming on August 22, an M5.8 event with a maximum perceived intensity of VIII and resulted in two additional deaths and an additional $10 million in property damage. Repercussions of the sequence of earthquakes were still being felt in the damaged downtown area of Bakersfield well into the 1990s as city leaders attempted to improve safety of the surviving non-reinforced masonry buildings.
Following the event, a field survey was conducted along the fault zone with the goal of estimating the peak ground acceleration of the shock based on visually evaluating precarious rock formations and other indicators. Ground disturbances that were created by the earthquakes were surveyed, both in the valley and in the foothills, with both vertical and horizontal displacements present in the epicenter area; the strong motion records that were acquired from the event were significant, a reconnaissance report was recognized for its coverage of the event, how it set a standard for those types of engineering or scientific papers. Between 1983 and 1986, several ritual sex ring child abuse cases occurred in Kern County, resulting in numerous long prison sentences, all of which were overturned—some of them decades because the prosecutors had coerced false testimonies from the purported child victims; the details of these false accusations are covered extensively in the 2008 documentary Witch Hunt, narrated by Sean Penn.
Kern county is considered to be a hotbed of country music the Bakersfield sound. The Buck Owens Crystal Palace is located in Bakersfield; the 2015 Disn