Since New Years Day Mount St. Helens has experienced 40 earthquakes within its vicinity as tremors continue every few hours. The most powerful earthquake was a magnitude 3.9 that occurred around midnight west coast time about 5 miles from Mount St. Helens and 23 miles from the town of Morton.
The 3.9 magnitude earthquake was felt in Portland but there were no reported injuries or damage. Since that earthquake there have been 16 more earthquakes, averaging about every half hour with magnitudes from 0.6 to 2.6.
It is common to experience swarms of earthquakes at Mount St. Helens. While it is certainly not a sign of an impending eruption, the earthquakes are a result of an active volcanic system.
Mount St. Helens is most commonly known for its major eruption in 1980, the deadliest and most economically damaging volcanic event in the history of the United States. The stratovolcano is situated just 96 miles from Seattle and 50 miles from Portland, making an eruption especially dangerous.
Google Imagery / TerraMetrics
While Mount St. Helens hasn't had a significant eruption for the past almost 38 years it is still considered an active stratovolcano by geologists. In fact, Mount St. Helens is considered a relatively young volcano, forming in the past 40,000 years and has been the most active volcano in the Cascade Range within the past 10,000 years.
This mountain range, along with Mount St. Helens, will continue to experience active volcanism and deadly eruptions as long as the Juan de Fuca Plate is subducting underneath the North American Plate. The dense, relatively thin, and low lying Juan de Fuca Plate is being pushed against and under the thicker and less dense North American Plate. This is due to the continuous spreading and opening of the Pacific Ocean, which has resulted in the Pacific Ring of Fire.
Wikipedia
While the recent earthquakes may make residents nearby Mount St. Helens uneasy, there is no immediate danger of an eruption. However, this is another sign of why we need constant volcano and earthquake monitoring.
With modern monitoring systems and subsurface modeling, geologists and geophysicists are able to build a 3-dimensional picture of volcanoes such as Mount St. Helens. The constant input of data, from seismic activity to precise topographical changes allows better prediction of a future event. While we can't be certain, chances are the next time Mount St. Helen erupts, we will be significantly better prepared.
San Francisco (CNN) A 4.4 magnitude earthquake struck early Thursday in Berkeley, California, according to a preliminary report from the US Geological Survey, jolting some residents of the densely populated San Francisco Bay area awake in their beds.
The earthquake hit at 2:39 a.m. local time (5:39 a.m. ET), centered near the Berkeley-Oakland boundary.
There were no immediate reports of damage in the area, the state Governor's Office of Emergency Services said.
No reports of damages from the region at this time. #earthquake #whatsshakincalifornia https://t.co/cSPgzjoMb5 — Cal OES (@Cal_OES) January 4, 2018
Some residents in the area told CNN affiliate KPIX that the quake shook them awake. A quake of this intensity generally would produce moderate shaking felt by nearly everyone near the epicenter, awakening many people and having the potential to break some windows and dishes, the USGS says
"It shook our house and shook the bed big time," Gina Solis of San Rafael, across the San Francisco Bay from Berkeley, told KPIX
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A magnitude 4.5 earthquake shook up the San Francisco Bay Area early Thursday.
It was felt throughout the region, and could be felt for perhaps five to 10 seconds. Near the San Francisco International Airport, several jolts could be felt.
The earthquake was centered along the Oakland-Berkeley border, just north of the Claremont Hotel. The epicenter of the earthquake is in the area of the Hayward fault, one of the most feared in the Bay Area, which could produce a magnitude 7 or greater earthquake and is directly underneath heavily populated areas.
A magnitude 4.5 earthquake is not expected to cause major damage, said U.S. Geological Survey seismologist Robert Sanders. Still, “there’s always a possibility of some minor damage to older structures in the area.”
The shaking was strong enough to wake people up when the earthquake hit at 2:37 a.m. One person in San Francisco said it was strong enough to knock picture frames from the wall.
The earthquake was felt as far away as San Francisco, Marin County, Sonoma County and Silicon Valley. Some Bay Area residents reported that the earthquake woke them up.
The Hayward fault courses right underneath Berkeley, Oakland, Hayward and Fremont and produces a large earthquake, on average, every 160 years, with a margin of error of about 80 years. It has been 150 years since the Hayward fault last ruptured, unleashing a huge earthquake.
The Hayward fault’s most memorable earthquake in recorded history was in 1868, and is estimated to have been a magnitude 6.8 earthquake — rupturing 20 miles of the fault’s length between San Leandro to what is now the Warm Springs neighborhood of Fremont, according to the USGS. It killed about 30 people and caused immense property damage, including the collapse of the Alameda County Courthouse’s second floor and heavy damage at the historic Mission San Jose adobe church in southern Fremont.
The Hayward fault is considered one of the nation’s most dangerous faults because it is located directly under the urban centers of the East Bay, including Memorial Stadium at UC Berkeley and a now-shuttered building that formerly housed Hayward City Hall, which is slowly being torn up by fault movement.
A USGS scenario for a 7.0 earthquake on the Hayward fault envisions it rupturing for 52 miles from San Pablo Bay to Fremont. It would cause one side of the fault to move four feet from the other. Many buildings, including apartments, still sit directly on top of the fault line, and were built before a state law passed in 1972 prohibiting new construction or substantial renovation on top of earthquake faults.
On its website, the USGS calls the Hayward fault the region’s “tectonic time bomb,” which could “cause hundreds of deaths, leave thousands homeless and devastate the region’s economy.”
In 2016, David Schwartz, a U.S. Geological Survey geologist, said in an interview that above the Hayward fault are “two million people who directly live on top of it. It sits geographically in the center of the Bay Area. There’s a tremendous amount of infrastructure built up on it — water systems, gas, electrical, BART crosses it — so a large event on that fault is like hitting the bull’s eye on a target.”
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ron.lin@latimes.com
@ronlin
UPDATES:
3:35 a.m.: Updated with context about the Hayward fault.
3:10 a.m.: Updated with locations where the earthquake was felt.
3:02 a.m.: Updated with quote from a USGS seismologist.
This article was originally published at 2:55 a.m.
