The last Big One ripped through Southern California in 1857, when an estimated magnitude 7.9 quake ruptured 200 miles of fault between Monterey and San Bernardino counties. But it wasn't a wall-to-wall quake: It stopped around the Cajon Pass, near the present-day 15 Freeway, probably because the fault south of that area had shaken just a few decades earlier, in 1812, Jones said. Because the 1812 quake had relieved tectonic tension in the Cajon Pass, it effectively stopped the 1857 quake from moving farther south.
"Can I imagine the 1857 earthquake happening again and stopping at the Cajon Pass? Probably not," Jones said. "Once you have a big slip, you're more likely to move along down the fault," she said. "If the rupture has been made ... that's a lot of momentum that will keep the rupture moving down the fault."
A magnitude 8.1 wall-to-wall quake would release twice the energy of the 1857 temblor, Jordan said.
On December 8, 1812, a powerful earthquake registering +7.0 occurred on the Mojave segment of the San Andreas fault.
Radiocarbon dating of the peat-layers revealed the ages of the sediments and therefore the approximate ages of the earthquakes that caused the fault ruptures. The geologist's data showed at least 5 very strong (M+7?) earthquakes had during the past 500 years with the approximate ages of: 1857, 1812, 1690, 1610, and 1470.The key to sequence are the 1857 and 1812 earthquakes, the last major earthquakes along the southern San Andreas fault during historic time!
The data suggests average time between very strong events is 97 years, with the greatest being 140 years and the shortest in just 45 years. Disturbingly, it has been 140 years since this segment last ruptured!
Another damaging earthquake occurred in southern California in the month of December, 1812, potentially triggered by the Wrightwood quake two weeks earlier that month. The epicenter of this one, too, is of uncertain location.
Because of the widespread damage it caused, it was probably as large as magnitude 7. It is probable that the epicenter was located offshore, possibly in the Santa Barbara channel, but an inland epicenter, somewhere in present-day Santa Barbara County, or even Ventura County, cannot be ruled out.
Originally posted by MamaJ
reply to post by MariaLida
Do you think the one in 1812 had anything to do with the New madrid fault? Do you think if one goes the other will?
The states seem to be very active lately and I am wondering if its because of fracking or what??
The Elsinore Fault Zone is a large right-lateral strike-slip geological fault structure in Southern California. The fault is part of the trilateral split of the San Andreas fault system and is one of the largest, though quietest faults in Southern California
It is estimated that this zone is capable of producing a quake of 6.5–7.5 Elsinore Fault Zonei
The Laguna Salada Fault is a probable southern continuation of the Elsinore Fault Zone in Southern California. These faults are considered to be secondary cohorts of the San Andreas Fault, and as such share some of the strike-slip motion between the North American Plate and the Pacific Plate. Laguna Salada Fault
Originally posted by MamaJ
reply to post by MariaLida
Thank you for the information and taking time to respond. Much appreciated. Again, we see the states active in and around the west. Oregon is on board this morning.
Anytime Vanuatu shows up it seems there is a bigger EQ. Have you notice that or am I just seeing into things and being paranoid. lol
Also 2 min later very interesting and rare EQ, no history from EMSC for EQ's in this area .. 2013-03-24 17:28:23.014 min ago 11.91 N 60.02 W 30 4.8 TOBAGO REGION, TRINIDAD-TOBAGO
Wednesday will mark the anniversary of the 1964 Alaska earthquake that generated the largest and best-recorded historical tsunami on the southern Washington coast.
Coinciding with the anniversary, March 24-30 is Tsunami Preparedness Week.
According to Deputy Director of Emergency Management Chuck Wallace, the entire Washington coast is susceptible to tsunami and there is much evidence of numerous large tsunami events that impacted our coastal counties.
Residents are asked to learn the risks they face at home and at work. Family preparedness will help reduce the impact any significant severe disaster will have upon all members of your family.
Blind thrust faults may trigger high-magnitude quakes in known risk zones, including the Newport-Inglewood fault, UCI geologists say.
Originally posted by MariaLida"Ok I will post some dangerous days for strong seizmic activity for rest of 2013, that days can effect San Andreas fault to rupture in very strong EQ .."
"Also dangerous location from Japan - China - Turkey - Italy to have very strong EQ's with many casualties .."
"Next days to end of April (next 35 days) and days from 16 to 23 June, also we will have super full moon for this year on 23 June .. "
"I expect at sensitive area very strong EQ of M 8.0 + from 16 to 23 June, for next 35 days we have several very dangerous days so I will post danger for all 35 days and we probably will have very strong seizmic activity worldwide and probably EQ of M 7.5 + .."
A: The San Jacinto fault commonly has a fairly significant level of micro-seismicity, so this is not unusual. This activity will grab my attention if it is followed by a moderate earthquake in the magnitude 5 range, which could be leading to a larger earthquake. As always, it is good to be prepared, just in case.
To expand a bit on this. The southern San Andreas fault last ruptured in a great earthquake about 300 years ago, and has an average recurrence interval for the past 1400 years of about 200 years - hence, the reason scientists keep on expecting a large earthquake on the San Andreas. In comparison, the large San Jacinto earthquakes that fall in the 7.3-7.5 range occur every 200-250 years, and the last one was in November, 1800.