![]() ![]() The zone of deformation between the Pacific and North American plates extends east into the Basin and Range Province of Eastern California and western Nevada. The San Andreas Fault (SAF) system is a network of active right-lateral strike-slip faults that form a portion of a complex and diffuse transform type plate boundary. Details that made their way into the earthquake catalogs showed that the period 1836–1840 was one of the most active on record. Instruments capable of detecting earthquakes that were designed by John Milne became available by 1896, but it was not until the Wood-Anderson seismograph was developed in 1926 that instruments began to be used in widespread fashion in California. Had there been equipment available to use in the study, there were still no scientists in the area to perform the work. The science of seismology was still many decades in the future and no measuring equipment existed to aid in the recording and documentation of earthquakes. The lack of archives made work difficult for seismologists preparing earthquake catalogs or those involved in creating seismic hazard and risk estimates. These records were tapped later on by seismologists in their study of earthquakes in the area. The California Gold Rush ushered in a host of changes, including the startup of newspapers in the Sierra Nevada and the San Francisco Bay Area. Beginning in 1833, the secularization of the Spanish missions brought an end to the once plentiful and dominant source of information in the study of previous earthquakes, and other Mexican sources during this period were also lacking. There were no local newspapers and no correspondents from news agencies in the distant United States. Indians kept no records and communications between the villages was poor. This is true even for the area between the San Francisco Peninsula and south to the Santa Clara Valley. See also: History of California before 1900, Ranchos of California, and Timeline of the San Francisco Bay Areaĭuring the 1830s in California, the largest of the few settlements usually contained no more than several hundred individuals. ![]() There is no evidence that a large earthquake hit the region in 1836. įor years, another large earthquake was said to have occurred two years earlier on Jalong the Hayward fault however, this is now believed to be referring to the 1838 San Andreas earthquake. Based on geological sampling, the fault created approximately 1.5 meters (5.0 feet) of slip. It is unknown whether there were fatalities. The region was lightly populated at the time, although structural damage was reported in San Francisco, Oakland, and Monterey. It was a strong earthquake, with an estimated moment magnitude of 6.8 to 7.2, making it one of the largest known earthquakes in California. It affected approximately 100 km (62 miles) of the fault, from the San Francisco Peninsula to the Santa Cruz Mountains. The 1838 San Andreas earthquake is believed to be a rupture along the northern part of the San Andreas Fault in June 1838. ![]()
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