page_title: Hayward Fault Zone
section_title: Rodgers Creek Fault Zone
hierarchical_section_title: Hayward Fault Zone / Tectonic setting / Rodgers Creek Fault Zone
caption_attribution_description: English: Major California faults and ages of volcanics
context_page_description: The Hayward Fault Zone is a geologic fault zone capable of generating destructive earthquakes. This fault is about 74 mi long, situated mainly along the western base of the hills on the east side of San Francisco Bay. It runs through densely populated areas, including Richmond, El Cerrito, Berkeley, Oakland, San Leandro, Castro Valley, Hayward, Union City, Fremont, and San Jose.
  The Hayward Fault is parallel to the San Andreas Fault, which lies offshore and through the San Francisco Peninsula. To the east of the Hayward lies the Calaveras Fault. In 2007, the Hayward Fault was discovered to merge with the Calaveras Fault east of San Jose at a depth of 4 miles, with the potential of creating earthquakes much larger than previously anticipated. Some geologists have suggested that the Southern Calaveras should be renamed as the Southern Hayward.
  North of San Pablo Bay is the Rodgers Creek Fault, which was shown in 2016 to be linked with the Hayward Fault under San Pablo Bay to form a combined Hayward-Rodgers Creek Fault that is 118 miles long, stretching from north of Healdsburg through Santa Rosa down to Alum Rock in San Jose.
context_section_description: The connection between the Rodgers Creek Fault Zone and the Hayward Fault Zone was unclear until 2015 when a survey of the floor of San Pablo Bay found that the ends of the two faults were smoothly linked between Point Pinole and Lower Tubbs Island. An alternate prior hypothesis suggested that the Hayward Fault and Rodgers Creek Fault were probably connected by a series of en echelon fault strands beneath San Pablo Bay. The new finding means that the Rodgers-Hayward system together could produce a quake with a magnitude as high as 7.2.  It is also considered possible that a major seismic event on either fault may involve movement on the other, either concurrently or within an 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).
  In October 2016, scientists found definitive evidence that the Rodgers Creek Fault and the Hayward Fault are linked together under San Pablo Bay.  A simultaneous rupture of the connected Hayward-Rodgers Creek Fault – about 118 mi (190 km) long from just north of Healdsburg down to Alum Rock in San Jose – could result in a major earthquake of magnitude 7.4 that "would cause extensive damage and loss of life with global economic impact".  It has been suggested that the name "Rodgers Creek Fault" be retired and that the entire 118 mi (190 km) fault be known as the "Hayward Fault".
caption: Geologic map of the Rodgers Creek Fault
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