On May 25, 1980–nearly one week after the spectacular eruption of the Mount St. Helens volcano–at 9:33 a.m. PST, a magnitude 6.0 earthquake rocked through Mammoth Lakes, California.
During the next 16 minutes, four more shocks, magnitude 4.1 – 5.5 followed. This seismic activity was the beginning of an earthquake sequence that produced 72 magnitude 4.0 to 6.3 shocks during the next 48 hours. Four of those were in the magnitude 6.0 range.
Damage from earthquake shaking included broken windows and water mains, cracked plaster, and fallen chimneys. Residents reported extensive destruction to breakable household items. Initial calculations of losses to schools and other public buildings and roads in the area were estimated to be $2 million (1980 dollars), which is about $6.2 million today.
Landslides and rockfalls were widespread. Large dust plumes could be seen over the Sierra Nevada immediately following the larger shocks. Two hikers in Yosemite Valley, nearly 45 miles away, were severely injured by rockfall. Roads were closed by debris.
With the Mount St. Helens eruption fresh on everyone’s mind, strong concerns that the quake sequence would be followed by a volcanic eruption in the Mammoth Mountains spread throughout the community. News media went crazy. Tourism and property values took a hit.
California Geological Survey (CGS) seismologists (then known as California’s Division of Mining and Geology) had been monitoring the area since a 1979 seismic event and had established a small network of sensitive instruments that were in operation when the earthquake sequence occurred.
Five hours after the first shocks, several CGS seismologists from field offices all over the state were dispatched. The team worked feverishly to add six more seismographs to the network, bringing the total to nine. They quickly retrieved film records and reloaded accelerographs with fresh film to monitor the ongoing activity. In all, 14 Strong Motion Instrumentation Program accelerographs were triggered by the three-days of activity. Several CGS geologists were sent out to map fault rupture.
The team also investigated other geologic impacts on the earthquake sequence, including incidents of surface rupture – that is, underground faults breaking the earth’s surface – for Alquist-Priolo Special Studies Zones to protect public safety and property in future events.
An earthquake clearinghouse was established as a base for scientists to gather, share information, and establish priorities for study and mapping. Local government officials, news media, and concerned citizens in the community also frequented the clearinghouse.
Ultimately, the earthquake sequence led to the establishment of the Long Valley Volcano Observatory to monitor the region. That eventually grew into the USGS’ California Volcano Observatory, which monitors the activity of all volcanic areas in California.
Today, the Department of Conservation’s Strong Motion Instrumentation Program has more than 1,000 accelerographs throughout the state monitoring significant seismic activity. The digitally collected data is used to inform future building codes, for earthquake early warning, and to help guide emergency responders to the hardest-hit areas after big earthquakes.
More detailed geologic information can be found in archived California Geology magazine articles on the conservation.ca.gov website.
|Quake sequences such as those in the Mammoth area mentioned in this story are infrequent but can occur in many parts of California. Learn to prepare at scec.org/learn
|What to do in an Earthquake
California Department of Conservation administers a variety of programs vital to California’s public safety, environment and economy. The services DOC provides are designed to balance today’s needs with tomorrow’s obligations by fostering the wise use and conservation of energy, land and mineral resources.
8 Comments Add yours
Do you see a connection between quakes in East Side CA (like now June 2920) being a precursor to eruptions of Mt St Helens in Oregon?
Hello, thanks for reading! According to our geologists, there is no connection between the recent eastern California earthquakes and volcanic eruptions at Mount St. Helens. These earthquakes are in a very different tectonic environment and at great distances from Mount St Helens.
I was on the chairlift to ski Mammoth Mountain’s cornice, about 100 ft from the terminus, when the quake hit. It was unlike any I’d felt before. It had been a warm morning but about 5m before the event occurred the wind changed direction/intensity and felt significantly (ten to fifteen degrees) colder. About 10 seconds prior the wind died and everything went muffled, almost silent. I felt a strong jolt then massive shaking/vertical up thrusting that caused the chairlift to swing from the 6 o’clock position to the 8 o’clock and 4 o’clock positions. The lift operator bounced around the cage like a corn kernel in an air popper. We watched the cornice give way in a small avalanche and could see boulders/snow give way. It took ski patrol about 40m to bring us down from the chairlift. We spent the next 3d sharing our room with 10 other skiers (ours was one of the few that was intact plus had a fireplace) while incredibly strong aftershocks hit. Highway 395 was closed due to avalanches so we had no choice but wait until it was cleared. The ground seemed to have a constant vibration that would crescendo and decrescendo rapidly but seemed different then then sound/motion of the aftershocks.
As people left the ski resort and drove back into town we watched as about 10-15 people stopped at the site of the Park’s Service EQ fault. Everyone swarmed in to see what changes the quake caused until the aftershocks hit. I’ve never heard people scream that loud lol! It seemed a Darwin Test to me-stay out of the railing free fault unless you’re wearing safety gear…..the rangers closed it as we watched.
I have 2 ???’s:
Would the P wave cause the apparent wind shift/temperature change?
Was the sensation of a constant vibration that the aftershocks flowed on top of due to infrasound or ???
That was one crazy day in my quake history as a native So Californian! Never had I felt the ground continuously shaking for hours like that!
I’m glad I had the experience, though. It taught me to have a deeper respect for Mother Earth than I already had & spurred me on to become more educated about geology.
My ex & our two young children & friends were camping in Iris Meadows campground, just over the hill from Convict Lake. The boys & the friend’s wife went fishing in the creek, while I took the kids & went down the hill to Tom’s Place to call my mom in Huntington Beach. The odd thing about that ride down the mountain was that there was a herd of deer gathered in a clearing. I had never, ever seen that before as a seasoned hiker & camper! They knew instinctively something bad was coming! Pre-shocks? Within a minute on the phone, the ground started to shake. But what was even more frightening was the sound coming from the ground, like a huge, low flying passenger jet; very deep rumble. I jumped out of the old telephone booth in time to see pickup size boulders bumping down the mountains. The kids were naturally scared. Living all of my life in California, I know about & have experienced earthquakes. NO ONE EVER GETS USED TO THEM! But this quake & aftershocks were different in that it seemed as though the ground never stopped shaking. The whole valley down the grade was filled with dust! I thought..Oh God, Hanta Virus! We waited until 9 pm for things to settle down, but that never happened. We packed up & made the long trip home through the desert at night. I was very glad we did as I later heard the quake(s) were due to magma movement. With a place like the Long Valley Caldera, you just never know for sure.
But man….what an experience that was! My kids who are in their 40s now still talk about it.
We lived in the OC growing up and my father had built a vacation cabin on Ridgecrest Dr. in 1970. We loved it up there so much, even after he broke his leg skiing under the lift poles of chair 2, that he decided to take his developer/investor skills up to take advantage of what he believed would be the new mecca of Skiing with nothing but cash profits aplenty. His first of what he figured would be many developments was just finishing the initial construction, Hidden Valley Condos Phase II. He had in fact finished one of the buildings with a 2-story loft unit that he intended to keep for us as a vacation home (Unit #118) with the other finished units to be used as models for the sales office.
We were finishing up Breakfast May 25th and decided not to ski that day because we had planned on spending the week up there, so no reason to fight the crowds…. Then the first one hit and my mother screamed at us kids to get into the doorways as she dove under the table…., I was 14 at the time…. but my dad just sat on the couch smiling. He said… Honey, I built these condos and there are I-beams that are embedded into the granite below the surface…. If this condo collapses, there is not a doorway or table in the world that is going to save us so just enjoy the ride….. I looked up and saw the undulation of the ceiling in the corner and watched as what seemed to be a foot of the I-Beam appeared to disappear and reappear as it moved in and out of the ceiling while the condo flexed with the quake.
Unfortunately that was the last time he smiled about earthquakes in Mammoth because by the time the sales office had opened, reports were already circulating that Mammoth was a Volcano and ready to blow at any minute…. He held on as long as he could, pun kinda intended, but ultimately had to let half the units go back to the bank because he just could not sell them. After that he never went back to Mammoth, not even to vacation or ski. He never forgave the USGS for what they did/said, although to be fair, as is normally the case the news media did blow it way out of proportion, again pun intended.
I went back a few times to ski with friends in the mid-late 80’s but have only been 2x since with the last being 2004, but then it got just too expensive to even look at the mountain, and I have not been back since. I will always cherish the memories of dashing through the snow barefoot from the indoor pool at HVCII back to the condo, tobogganing/sledding/tubing down the hill next to the Ridgecrest Dr property, and fishing up in the lakes. If nothing else, it gave us one hell of a wild ride.
What a great comment, Todd. Thank you for reading and for sharing your memories with us! If you are on Instagram or Twitter, the California Geological Survey is on both for more history and info @CAGeoSurvey. Thanks again!
I’m also here in OC in HB, & was up in Convict Lake for that event.
My comments are above yours on this page.
I have come to the Eastern Sierra all of my life to fish & camp, but nothing
could have prepared me for the quakes that day.
Quite an experience that I’ll never forget, though as CA natives, we know to expect quakes, & to be prepared for them. That series of quakes whet my appetite to learn more about volcanology & just geology in general over the past 40 yrs.
Thanks to Dr. David Gallo, late of Wood’s Hole Oceanographic Institution in Massachusetts, I have learned not to fear, but to be alert & prepared.