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1838 San Andreas earthquake
Based on the seismic activity events, a missionary built prior to 1836 and San Francisco Bay did not experience any evidence of faulting, until 1838. Therefore, 1838 earthquake was mistaken for the date 1836.[1] There is evidence of the fault rupture extending to Monterey because the aftershocks reached San Juan Bautista, not limited to Oakland. The rupture extending to San Francisco to San Juan Bautista had a length totaling ∼ 140 km and indicating an M ∼ 7 : 4 earthquake.[2] The several coastal cities were destroyed including Carmel, Santa Cruz, and San Francisco Bay.
At both sides of San Francisco the shaking was felt, residents were injured. Even adobe homes were not able to withstand the intensity of fault rupture. Although it was believed that the 1836 was the main earthquake, it disregarded the aftershock in 1838, as the aftermath of destructive effects being greater than the prominent known earthquakes from San Andreas Fault. Sightings of earthquake destruction were described partially in the Sonoma Democrat, 14 October 1865 article: It was unquestionably the most severe that has been experienced since the advent of Americans here, but not comparable to the one which occurred about the year 1838, which shook down thick walled adobe houses, and caused mountain sides to slide down. [3]
According to the earthquake intervals being 68 years, following 1838, was the historic San Francisco earthquake in 1906. Three earthquake events occurred with a magnitude greater than 6, one was the June 1838 extending from the Peninsula to the Santa Cruz and Monterey Bay region.[2] It had a greater intensity at Monterrey and San Francisco region.
History of Faulting incidents
editEarthquake ruptures along Hayward fault and San Andreas Fault
editNot to be mistaken, the Hayward fault 1836 earthquake was speculated to have the similar effects of the San Andreas Fault earthquake. The Hayward Fault was reported in the affected cities: Santa Clara, and the East of San Francisco Bay.[1] Prior to 1838 and the inception of 1776 Mission San Francisco Dolores, there had been no reported evidence of earthquakes. The post 1600 earthquake ruptures along several faults were depicted by records of the infrastructure in missions damaged, which were historically significant for evaluating evidence of earthquakes in the San Francisco Bay Area[4] The previous stress fractures were inferred in 1650-1770, while the M <7 was between 1776 and 1836.[5] The speculation of the 1836 earthquake occurring at the North Hayward area were small shocks. The eruption of the Hayward fault in 1868 derived from the stress concentrated in the Hayward fault during 1838.[5]
Reports of experienced earthquakes
editIn June 1838, ground rupture probably occurred on the San Andreas fault at least from near Lone Mountain, south of San Francisco, toward Mission Santa Clara. [1]The earthquake was destructive in the East Bay at San Leandro and Mission San Jose. The faulting was narrated as a greater intensity than the 1906 earthquake, due to its damages to redwood trees and large extent aftershocks felt in Oakland and Monterrey. Due to the numerous widely felt aftershocks, the rupture along Hayward fault was probably influenced by the San Andreas fault earthquake[1] and not indicative of being 1836, as no reported damage was indicated by people living near Oakland. While memoirs evidently appeared in the newspaper following the 1868 Hayward earthquake, the 1838 earthquake was narrated as a more destructive earthquake than the 1868.
Sightings of earthquake destruction of East Bay were described partially in the Sonoma Democrat, 14 October 1865 article: It was unquestionably the most severe that has been experienced since the advent of Americans here, but not comparable to the one which occurred about the year 1838, which shook down thick walled adobe houses, and caused mountain sides to slide down.At that time the adobe house of Estudillo, an old settler in Alameda county, was thrown down and a large portion of a mountain side, near San Leandro, gave way and slid down to its base. The place where the slide occurred is plainly visible from the town of San Leandro. But the shaking up we received, last Sunday [8th], was quite sufficient to satisfy the present inhabitants. The amount of damage must be very large, though it will probably never be known. Besides a number of buildings which were ruined [in San Francisco], there are a great many others badly cracked and otherwise injured. [3]
Intensity Earthquake
editThe 1838 San Andreas earthquake was a fault rupture that extended from San Francisco to San Juan Bautista. Since the South Francisco Bay is at the center of three plate boundary fault zones, many occurrences of earthquakes of magnitude <7 were recorded. The intensity of the earthquake had magnitude 7 ½ and extended to the Hayward fault. There is evidence of the fault rupture extending to Monterey because the aftershocks reached San Juan Bautista and Oakland. The rupture extending to San Francisco to San Juan Bautista had a length totaling ∼ 140 km and indicating an M ∼ 7 : 4 earthquake.[2] It also caused two large aftershocks in 1840 and 1841. Toppozada and Borchardt (1998) compile damage reports of the extent of faulting in this event, as reported by Louderback (1947), and report strong intensities in Woodside, where solid adobe houses were cracked severely and redwoods were “broken off and hurled.”[2] Its damaging effects are due to its proximity to the several faults along the San Andreas Fault. Paleoseisimic suggest that the June 1838 earthquake had a mercalli intensity XI and that its rupture was along the San Francisco Peninsula, but it did not go past the Santa Cruz Mountains to the extent of the Grizzly Flat area.[6] Even though studies have measured stress patterns comparing the deformation along fault segments, there is no precise location to the total extent of these earthquake ruptures. North of Grizzly Flat was detected to experience a 7.1 magnitude and there was not a surface slip, despite it being on the San Andreas Fault.[5] The strike slip ranged from Magnitude ~6.8- ~7.5 as evidence maps its inconsistent stress patterns distributing out from the Santa Francisco Bay Area.
References
edit- ^ a b c d Toppozada, T., & Borchardt, G. (1998). Re-evaluation of the 1836 "Hayward fault" and the 1838 San Andreas fault earthquakes. Bulletin Of The Seismological Society Of America, 88(1), 140-159.
- ^ a b c d Streig, A., Dawson, T., & Weldon, R. (2014). Paleoseismic evidence of the 1890 and 1838 earthquakes on the Santa Cruz Mountains section of the San Andreas Fault, near Corralitos, California. Bulletin of the Seismological Society of America, 104(1), 285-300.
- ^ a b Toppozada, T., & Borchardt, G. (1998). Re-evaluation of the 1836 "Hayward fault" and the 1838 San Andreas fault earthquakes. Bulletin Of The Seismological Society Of America, 88(1), 149.
- ^ Schwartz, D. P.; Lienkaemper, J. J.; Hecker, S.; Kelson, K. I.; Fumal, T. E.; Baldwin, J. N.; Seitz, G. G.; Niemi, T. M. (2014), "The Earthquake Cycle in the San Francisco Bay Region: A.D. 1600–2012" (PDF), Bulletin of the Seismological Society of America, Seismological Society of America, 104 (3): 1299–1328, Bibcode:2014BuSSA.104.1299S, doi:10.1785/0120120322
- ^ a b c Pollitz, F., Bakun, W., & Nyst, M. (2004). A physical model for strain accumulation in the San Francisco Bay region: Stress evolution since 1838. Journal of Geophysical Research: Solid Earth, 109(B11)
- ^ Paleoseismic studies of the San Francisco Peninsula segment of the San Andreas Fault zone near Woodside, California. (1999). Journal of Geophysical Research: Solid Earth, 104(B10), 23,231