Difference between revisions 113734844 and 113734845 on dewiki

[[Image:122-38HaywardFault.jpg|thumb|300px|For recent activity in the region shown on this map see [http://quake.wr.usgs.gov/recenteqs/FaultMaps/122-38.htm the USGS map for this location.] With appropriate browser settings the "live" maps will also show all of the names of faults shown on the map as you rollover with the cursor.]]

The '''Hayward Fault Zone''' is a [[geologic fault]] zone capable of generating significantly destructive [[earthquake]]s. About 60 kilometers long, it lies mainly along the western base of the hills on the east side of [[San Francisco Bay]].   It runs through densely-populated areas, including the cities of [[Richmond, California|Richmond]], [[El Cerrito, Contra Costa County, California|El Cerrito]], [[Berkeley, California|Berkeley]], [[Oakland, California|Oakland]], [[San Leandro, California|San Leandro]], [[Hayward, California|Hayward]], [[Fremont, California|Fremont]], and [[San Jose, California|San Jose]].

The Hayward Fault is parallel to its more famous (and much longer) westerly neighbor, the [[San Andreas Fault]], which lies offshore and through the San Francisco peninsula. To the east of the Hayward lies the [[Calaveras Fault]].   The Hayward Fault merges with these two fault systems south of San Francisco Bay.

North of [[San Pablo Bay]], and somewhat offset from the Hayward Fault is the '''Rodgers Creek Fault''', considered by many to be an extension of the Hayward Fault Zone.   Another fault further north, the [[Maacama Fault]], is also considered to be part of the "Hayward Fault subsystem". <ref>[http://www.storage.water.ca.gov/docs/o_reg_geo_plate_faulting.pdf p.26]</ref><ref>[http://gsa.confex.com/gsa/2005CD/finalprogram/abstract_85295.htm]</ref> 

While the San Andreas Fault is the principal [[transform fault|transform boundary]] between the [[Pacific Plate]] and the [[North American Plate]], the Hayward Fault takes up a share of the overall motion between the plates. 

==Tectonics of the Hayward Fault Zone==
:''Main articles: [[Seafloor spreading]],  [[Subduction]], [[Plate tectonics]], [[Geologic fault]], [[Earthquake]]''
[[Image:PlateMovementEaNoPac.png|thumb hay everybody|right|250px|Plate motions of the eastern North Pacific-North America region. The [[San Francisco Bay Area]] is in the middle of the diagonal green segment (showing slip&ndash;strike movement) near the center of the image. Red arrows indicate movement rates relative to the North American plate]]
The [[Pacific Plate]] is a major section of the earth's crust, gradually [[Seafloor spreading|expanding]] by the eruption of [[magma]] along the [[East Pacific Rise]] to the southeast.   It is also being subducted far to the northwest into the [[Aleutian Trench]] under the North American Plate well north of San Francisco.   In California, the plate is sliding northwestward along a [[transform boundary]], the [[San Andreas Fault]], toward the subduction zone. At the same time, the [[North American Plate]] is moving southwestward, but relatively southeast along the faultline.   The westward component of the North American Plate's motion results in some compressive force along the San Andreas and its associated faults, thus helping lift the [[Pacific Coast Ranges]] and other parallel inland ranges to the west of the [[Central Valley (California)|Central Valley]], in this region most notably the [[Diablo Range]].   The Hayward Fault shares the same relative motions of the San Andreas. As with portions of other faults, a large extent of the Hayward Fault trace is formed from a narrow complex zone of deformation which can span hundreds of feet in width.

As the [[transform boundary]] defined by the San Andreas Fault is not perfectly straight, and the motion of the [[North American plate]] is not entirely parallel to the plate boundary, movement along the boundary creates stresses in the crust on either side of the boundary, resulting in additional faulting on both sides of the San Andreas Fault. The Hayward Fault is one of the larger faults created this way, along with the [[Calaveras Fault]] and the [[San Gregorio Fault]]. 

===Rodgers Creek Fault Zone===
The '''Rodgers Creek Fault Zone''', is considered by many experts to be an extension of the Hayward Fault Zone.   However, the connection between the two faults is still unclear as they are not aligned under San Pablo Bay.   In fact, the Rodgers Creek Fault is actually aligned with the Pinole Valley Fault, not the Hayward Fault.   Nonetheless, the current view is that the Hayward Fault and Rodgers Creek Fault are probably connected by a series of ''en echelon'' fault strands beneath San Pablo Bay.   It is considered possible that a major seismic event on either fault may involve movement on the other, either concurrently or within a short interval of up to several months. The [[Association of Bay Area Governments]] has prepared ground shaking maps that include a possible concurrent scenario (these are shown below).
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[[Image:BayareaUSGS.jpg|thumb|right|250px|USGS Satellite photo of the San Francisco Bay Area. Light gray areas are heavily urbanized regions]]

==Notable earthquakes==
The largest quake on the Hayward Fault in ''recorded'' history occurred in 1868, with an estimated [[Moment magnitude scale|magnitude]] of 7.0.
   It occurred on the southern segment of the fault, receiving its name (some decades later) from the nascent town of [[Hayward, California|Hayward]] where it was determined the quake's epicenter was located.   However, the 1868 quake caused much damage throughout the then sparsely-settled Bay Area, including the city of San Francisco. [http://query.nytimes.com/mem/archive-free/pdf?res=9801E5DB1E3CE13BBC4A51DFB6678383679FDE][http://query.nytimes.com/mem/archive-free/pdf?res=9401E3D71039E033A25757C1A96F9C94649ED7CF]  In fact, the 1868 quake became known as the "Great San Francisco Earthquake" until the larger tremor in 1906.

The last truly major earthquake in the region was the [[1906 San Francisco Earthquake]] which occurred on the San Andreas fault. Many seismologists believe that the 1906 earthquake reduced the stress on many faults in the Bay Area including the Hayward fault, creating an "earthquake shadow": a quiescent period following a major earthquake.   Since the 1906 San Andreas event there have been no moderately strong earthquakes on the Hayward fault as were seen before that earthquake. It also appears likely that this quiet period in the earthquake shadow is ending, as projected by the rate of plate motion and the stress state of other faults in the region.

The following table chronologically lists all of the historic earthquakes on the Hayward Fault Zone which have exceeded magnitude 5.5. 

(contracted; show full)wed by huge urban wildfires compounded by damage to water systems or massive landslides in saturated soils. In addition to direct damage the effects on commerce due to damaged infrastructure would also be substantial. Experience with large area urban destruction such as caused by earthquake, hurricane, and firestorms has shown that complete rebuilding can take up to a decade, owing to various factors including disputes with insurance companies, a lack of qualified local builders, shortages of supplies, an 
an influx of contractors from outside of the region of dubious qualifications and with no incentive to maintain and enhance a local reputation.

The progressively more severe reports and estimates of event probability and consequences have awakened a broad interest in training people for emergency response. It is becoming widely understood that professional fire fighting, police, and medical services will be overwhelmed by a major event and that neighbors will have to assist each other as best they can. As of (contracted; show full)g of the highway and by differential movement of large sections. (More modern construction for these conditions employs linked and "floating" - in mud - lightweight [[concrete]] and plastic foam box structures to support a road.) Similar conditions underly the eastern approach roads the Bay Bridge. Better, but still locally poor soils underlie the portion of [[Interstate 880 (California)|Interstate Highway 880]] that extends to the South Bay region from the eastern terminus of the [[San Francisco
- – Oakland Bay Bridge]]. As the bulk of cargo containers from the [[Port of Oakland]] travel on these two roads, the disabling of both would cause severe disruption of west coast import and export goods, owing to the consequent overloading of other West Coast container handling ports. Such disruption would be minor compared to that which could be produced by a large southern California earthquake, as the bulk of west coast container traffic is through the ports of [[Port of Long Beach|Long Beach]] and [[Port of Los Angeles|Los Angeles]].

'''Highway 580'''

A major route for commuters travelling from Southern Alameda County and the East Bay hills to downtown Oakland and San Francisco, [[Interstate 580 (California)|Interstate 580]] crosses the fault twice, and runs very close to the fault between the intersections with [[State Route 13 (California)|State Route 13]] (the Warren Freeway) and [[Interstate 238 (California)|Interstate 238]].

====Eastern span of the San Francisco- – Oakland Bay Bridge====
[[Image:EasternSFO OAKBrFromTI.jpg|thumb|left|200px|Eastern span and replacement construction]]
{{main|Eastern span replacement of the San Francisco- – Oakland Bay Bridge}}
The 1989 [[Loma Prieta earthquake]] caused a failure of a single section of the upper deck of the eastern span of the [[San Francisco- – Oakland Bay Bridge]], which closed the bridge for 30 days. Engineers and much of the public have long recognized that a strong earthquake centered closer to the bridge on either the Hayward or San Andreas faults could cause a complete collapse of the eastern span. A replacement eastern span is currently under construction, with completion projected for late 2013 (originally 2010).
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====Railroads====
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Gasoline is continuously shipped under pressure from Richmond and Martinez area refineries through [[Kinder Morgan Energy Partners]] pipelines which run under heavily populated East Bay urban areas to tank terminals near San Jose Airport in North San Jose. Aviation fuels are piped from these same refineries to the Oakland Airport. A number of spills have previously occurred due to landslides and such spill and related toxic and flammable material release may be prevalent in a major seismic event.
   A November 9, 2004, construction accident on this pipeline system in Walnut Creek killed five people.<ref>{{cite news| first = Henry | last = Lee | title = $6 million settlement in 2004 pipeline blast: 3 injured workers, dead man's kin to share funds | publisher = San Francisco Chronicle |date = 2006-10-20 | url = http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2006/10/20/BAG6TLST121.DTL | accessdate = 2006-01-23}}</ref> As seen in other worldwide pipeline ruptures, even an instantaneous (contracted; show full)
<ref>[http://www.quake06.org/quake06/best_practices/WSSIP.html EBMUD Water Supply Seismic Improvement Program]</ref>
<ref>[http://www.ktvu.com/news/11138463/detail.html Major East Bay Water Supply Line Retrofit Completed]</ref>

The [[Hetch Hetchy Aqueduct]], which supplies 270 to 315 million gallons of water per day to the City of San Francisco and other Bay Area communities, directly crosses the Hayward Fault in [[Fremont, California|Fremont]].
   A 2002 report by the Bay Area Economic Forum suggests that a breakdown in the aqueduct due to an earthquake could cut off Hetch Hetchy water to the Bay Area for 60 days.   In addition to depriving 85% of San Francisco residents of their drinking water, this would cut off supplies for firefighting and water-intensive industry, causing economic damage of $17.2 to $28.7 billion dollars.
<ref>[http://www.sfchroniclemarketplace.com/cgi-bin/article.cgi?f=/c/a/2002/10/09/BA139730.DTL&hw=quakes&sn=553&sc=099 San Francisco Chronicle, October 9, 2002: "$28 billion Hetchy loss in big quake"]</ref>

====Lake Temescal====
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[[Image:BandedRetroColumn.jpg|thumb|left|200px|[[State Route 24 (California)|State Route 24]] [[Seismic retrofit|retrofit]] at College Avenue Rockridge BART parking.<br>Jacketed and grouted column on left, unmodified on right]]
It is primarily the likelihood of a severe earthquake on the Hayward or San Andreas faults that has spurred a substantial effort to [[Seismic retrofit|retrofit]] and sometimes replace large structures at risk, particularly the eastern and western spans of the [[San Francisco
- – Oakland Bay Bridge]], the [[San Francisco City Hall|San Francisco]] and [[Oakland, California|Oakland]] city halls, and numerous elevated rail, road, and pedestrian structures and [[overpass]]es. Much work remains to be done in the region and progress is being hampered by budget constraints imposed by trickle down federal-state-regional deficits, design and construction delays due to state and local political bickering over design, and unexpectedly high [[steel]] and [[cement]] costs due to the extensive co(contracted; show full)==References==
* [http://gldims.cr.usgs.gov/webapps/cfusion/Sites/qfault/qf_web_search_res.cfm USGS Database]
{{reflist}}

==See also==
*[[Earthquake warning]]
*[[Earthquake prediction]]
*[[Eastern span replacement of the San Francisco
- – Oakland Bay Bridge]]
*[[Household seismic safety]]
*[[San Andreas Fault]]
*[[Seismic retrofit]]

==External links==
*[http://quake.wr.usgs.gov/research/geology/hf_map/  USGS Satellite Maps - Hayward Fault] This includes links to the Google Earth virtual tour of the fault.
*[http://eastbayexpress.com/issues/2005-02-16/news/feature_print.html   "It's Not Our Fault"', article in the ''East Bay Express'']
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[[Category:Geography of Contra Costa County, California]]
[[Category:Geography of the San Francisco Bay Area]]
[[Category:Napa County, California]]
[[Category:Solano County, California]]
[[Category:Seismic faults of California]]

[[fr:Faille de Hayward]]