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U.S. Earthquakes

  • 90+ Earthquakes Shake Yellowstone Lake within 24 hours

    The southwest side of Yellowstone Lake, the largest body of water in Yellowstone National Park, is experiencing quite an uptick in seismic activity today, Thursday, September 10.

    According to the United States Geological Survey (USGS), Yellowstone experiences about 1,500 to 2,500 located earthquakes per year, many occurring in swarms, or earthquakes that cluster in time and space. Most swarms are small, containing 10-20 earthquakes, and short, lasting for one to two days.

    Today's seismic activity is a little abnormal in that as of 4 pm Thursday, 93 earthquakes, and counting, have occurred all within this area of Yellowstone Lake since Wednesday night, according to USGS data. All but seven of the earthquakes have been under 2.5 magnitude. None have reached 3.0 magnitude.

    In the same area depicted in the map below, 108 earthquakes have been recorded over the past 30 days, including today's activity. That means only 15 earthquakes were recorded in the area before today.

    Image Above: The orange dots each represent an earthquake recorded in the area within the past 24 hours.

    WATCH 'Thunderous Roar' Reverberates Across Yellowstone Park Sparking Fears Among Visitors

  • Large Swarm of Earthquakes Strikes Southern California

    An intense earthquake swarm started near Salton Sea, California on September 30, 2020, with 421 earthquakes detected by 07:00 UTC on October 1.

    • The swarm is centered just southeast of Salton Sea, near Westmorland in Imperial Valley, in an area with a history of intense swarms. The most notable earthquakes in the region include M5.8 in 1981 and M5.4 in 2012.
    • During this earthquake swarm, the probability of larger earthquakes in this region is significantly greater than usual, the USGS said.
    • The swarm is taking place in Brawley Seismic Zone, a network of small faults that connect the San Andreas and Imperial faults.

    The USGS registered a total of 440 earthquakes from 10:06 UTC on September 30 to 07:33 UTC on October 1, 2020, with the largest M4.9 at 00:31 UTC on October 1, followed by M4.5, M4.4, M4.2, and two M4.1.

    "This earthquake [M4.9] and the associated swarm are located in an area of diffuse seismic activity between the San Andreas fault in the north and the Imperial fault to the south," USGS seismologists said in a statement.

    "This area has also seen swarms in the past – notably the 1981 Westmorland swarm, which included a M5.8 earthquake, and the 2012 Brawley swarm, which included a M5.4 earthquake. Past swarms in this region have remained active for 1 to 20 days, with an average duration of about a week. The current swarm is occurring about 40 kilometers (25 miles) to the south of the swarm that occurred near Bombay Beach in August 2020."

    According to the USGS, there is approximately a 3 in 10 000 chance of a magnitude 7+ earthquake in the vicinity of this swarm in a typical week.

    "[This is] one of the largest swarms we have had in the Imperial Valley," seismologist Dr. Lucy Jones said.

    "None of the earthquakes that have been happening in the Imperial Valley are anywhere near the San Andreas fault," Jones added.

    "They are in the Brawley Seismic Zone – a network of small faults that connect the San Andreas and Imperial faults. Historically largest Brawley event was M5.8."

    Scenarios

    The following three scenarios describe the possibilities of what could happen from September 30 to October 6, according to the USGS forecast released on September 30.

    Only one of these scenarios will occur within the next week, USGS said. 

    These scenarios include the possibility of earthquakes on and off the Imperial and San Andreas Faults.

    1. Scenario 1 (most likely): Earthquakes continue, possibly including earthquakes up to magnitude 5.4.

    The most likely scenario is that the rate of earthquakes in the swarm will decrease over the next 7 days. Some additional moderately sized earthquakes (M4.5 to 5.4) may occur, which could cause localized damage, particularly in weak structures. Smaller magnitude earthquakes (M3.0+) may be felt by people close to the epicenters.

    2. Scenario 2 (less likely): A larger earthquake (magnitude 5.5 to 6.9) could occur within the next 7 days.

    A less likely scenario is a somewhat larger earthquake could occur (up to M6.9). Earthquakes of this size could cause damage around the area close to the earthquakes that have already occurred and would be followed by aftershocks that would increase the number of smaller earthquakes per day. This scenario occurred in a previous swarm in the area – in 1981, when a swarm in this region included a magnitude 5.8 earthquake.

    3. Scenario 3 (least likely): A much larger earthquake (magnitude 7 or higher) could occur within the next 7 days.

    A much less likely scenario, compared with the previous two scenarios, is that the ongoing swarm could trigger an earthquake significantly larger than the M4.9 that occurred on September 30 (i.e., M7.0 and above). While this is a very small probability, if such an earthquake were to occur, it would have serious impacts on communities nearby and would be followed by aftershocks that would increase the number of smaller earthquakes per day.

    Featured image credit: TW/SAM, Google

  • M4.6 Earthquake Shakes Kīlauea Volcano, Widely Felt Across Hawaii

    At 11:20pm on Thursday, July 2nd (2020-07-03 09:20:01 UTC), a M4.6 earthquake shook the south flank of Kīlauea at a depth of about 4.2 miles.

    The estimated epicenter is within Hawaiʻi Volcanoes National Park beneath Pulama Pali, initially placed near the hairpin turn in the Chain of Craters Road.

    Reports have now come in from Maui, Lānaʻi, Oʻahu and Kauaʻi as well as shown on the map below.

    Those in the nearby Volcano communities report this as the heaviest shaking since 2018, perhaps due to proximity and shallower depth.

    Given its location and depth beneath the South Flank, this event falls into the post-2018 M6.9 grouping accommodating continuing flank movement.

    This does not on its own indicate any change in the non-eruption, but we will continue to monitor USGS feeds and reports for any changes warranting further public update.

    Two months ago, the USGS announced: We Don’t Want to be Alarmist, But we Also Need to Tell the Public That There Is an Increasing Possibility of Explosive Eruptions at Kilauea Volcano in Hawaii?

  • M5.1 Earthquake Shakes North Carolina, Strongest Since 1916

    A very shallow earthquake registered by the USGS as M5.1 hit Sparta, North Carolina, U.S at 12:07 UTC (08:07 LT) on August 9, 2020, causing widespread damage. The agency is reporting a depth of 3.7 km (2.3 miles). This is the strongest earthquake to hit North Carolina since M5.2 in 1916.

    The epicenter was located 4.1 km (2.6 miles) SE of Sparta (population 1 726), 43.5 km (27 miles) W of Mount Airy (population 10 354), and 59.5 km (37 miles) ENE of Boone (population 18 156), North Carolina.

    1 000 people are estimated to have felt very strong shaking, 5 000 strong, 20 000 moderate, and 568 000 light.

    More then 45 000 people submitted their "Did You Feel It" reports to the USGS in the first few hours.

    "The quake occurred as a result of oblique-reverse faulting in the upper crust of the North American plate," the USGS said.

    Focal mechanism solutions for the event indicate rupture occurred on a moderately dipping fault either striking to the northwest or south.

    This earthquake occurred in the interior of the North American plate -- intraplate earthquake. These are generally less common than interplate earthquakes that happen near tectonic plate boundaries.

    "Large earthquakes are relatively uncommon in the region directly surrounding this earthquake," USGS added.

    This earthquake was preceded by at least four small foreshocks ranging from M 2.1-2.6, beginning about 25 hours prior to the mainshock. and followed by M1.8 at 17:45 UTC.

    USGS scientists expect that this event will trigger aftershocks, but these will decrease in frequency over time.

    According to their forecast, there is a 1 % chance of one or more aftershocks that are larger than magnitude 5.1 over the next 7 days. It is likely that there will be smaller earthquakes over during the same period, with 0 to 11 magnitude 3 or higher aftershocks.

    Magnitude 3 and above are large enough to be felt near the epicenter. The number of aftershocks will drop off over time, but a large aftershock can increase the numbers again, temporarily.

    Residents around Sparta and other towns near the epicenter should prepare for aftershocks, which are usually more than a magnitude weaker than the mainshock. Aftershock sequences of M5.0 quakes can last many days and weeks

  • Major 7.8 Eathquake Strikes Alaska, Widespread Shaking Felt

    A powerful earthquake off Alaska’s southern coast jolted sparsely populated coastal communities late Tuesday…

    And some residents briefly fled to higher ground over fears of a tsunami.

    There were no immediate reports of damage in the Alaska Peninsula and the tsunami warning was canceled after the magnitude 7.8 quake offshore produced a wave of a less than a foot (30 centimeters).

    According to the U.S. Geological Survey, the earthquake struck Tuesday at 10:12 p.m. local time and was centered in waters 65 miles (105 kilometers) south-southeast of the tiny community of Perryville, at a depth of 17 miles (28 km).

    Because of the temblor’s location, some nearby Alaska Peninsula communities did not experience shaking that would normally be associated with the quake’s magnitude, said Michael West, Alaska state seismologist.

    Residents in some small towns within a hundred miles (160 kilometers) of the quake reported very strong shaking and some shaking was felt more than more than 500 miles (805 kilometers) away in the Anchorage area.

    The tsunami warning prompted coastal residents to evacuate to higher ground, with social media posts showing long lines of people fleeing towns like Homer and Kodiak as tsunami sirens wailed in the background.

    On Kodiak Island about 200 miles (320 kilometers) northeast of where the earthquake was centered, the local high school and the Catholic church opened their doors for evacuees and the school parking lot was declared a safe zone, with some people staying in their cars with pets until it was safe to go home.

    Officials at the National Tsunami Warning Center in Palmer, Alaska,began calling off the tsunami advisories and warnings after a wave of less than 1 foot (30 centimeters) was recorded in the community of Sand Point.

    I might have expected a little bit more water, but I’m happy that there wasn’t,” said David Hale, the senior duty scientist at the tsunami center.

    Now, watch the waves from the M7.8 Alaska earthquake roll across seismic stations in North America!

    Tuesday’s quake was more powerful than the magnitude 7.1 earthquake that caused damage in the Anchorage area in November 2018, although this earthquake released about 15 times as much energy as that earthquake.

    More than a dozen aftershocks of magnitude 4.0 or higher were reported immediately after the earthquake.

    We got people here who are going be working all night,” West said. ”These aftershocks will go and go and go and go.

    The earthquake happened in the so-called Alaska-Aleutian Trench, where a magnitude 9.2 quake in 1964 was centered.

    That remains the second most powerful earthquake ever recorded globally. The temblor and ensuing tsunami caused widespread damage and killed 131 people, some as far away as Oregon and California.

    https://twitter.com/i/status/1285853240119250944

    Alaska is the most actively seismic U.S. state. Nearly 25,000 earthquakes have been recorded in Alaska since Jan. 1, according to the center. And it’s in the Ring of Fire!

  • Southern California is rocked by a 4.5-magnitude earthquake - with tremors felt from Los Angeles to San Diego

    A 4.5-magnitude earthquake rocked Southern California, with tremors felt from Los Angeles down to San Diego.

    The quake hit 10 miles west of L.A. at 11.39 pm local time on Friday, according to the US Geological Survey.

    It occurred at a depth of nearly 11 miles, and lasted for 30 seconds. It was reported to be one of the biggest earthquakes to hit the L.A. area in years.

    There have been no reports of injuries or damage to property, but authorities warned locals to prepare for aftershocks.

    The Los Angeles Fire Department posted a tweet shortly after the quake, which read: 'If Inside When Shaking Starts: DROP, COVER, HOLD ON! Protect Your Head & Neck While Taking Cover Under Sturdy Furniture or Near a Sturdy Interior Wall, Away From Windows and Doorways Until Shaking Stops.

    One seismologist stated that Friday's quake occurred in almost the exact same location as the Whittier Narrows earthquake in October of 1987.

    That 5.9-magnitude earthquake left eight people dead and a further 200 injured. The damage bill totaled more than $213 million.

    Meanwhile, on Friday night, several people posted videos that showed their homes shaking as the quake occurred.

    One TikTok user was partway through a performance, when her house began to rattle as the tremors hit.

    Another wrote on Twitter: 'Felt the biggest earthquake in Los Angeles yet. It was so big I ran out of my apartment with my purse and no shoes.'

    Residents live in fear of a giant earthquake jolting through the center of the city.

    Seismologists say a dormant fault line runs directly beneath Los Angeles that is well overdue for rupture.

    The experts fear the result could be a catastrophic 7.4-magnitude earthquake that would cause massive loss of life and billions of dollars in damage.

    It's been more than a generation since a giant earthquake shook the city.

    The 6.7-magnitude Northridge earthquake rocked the L.A's suburbs on January 17, 1994, causing more than $20 billion in damage and killing 60 people.

    'Hidden' fault line directly under Los Angeles threatens a devastating magnitude 7.4 earthquake

    A fault line, long believed to be dormant underneath Los Angeles, could link with others and cause a major magnitude 7.4 quake, according to a report published in September 2019.

    The 'Wilmington Fault,' was so deep below the Earth's surface that it was difficult to study, but researchers from Harvard, the USC and the US Geological Survey last year imputed a 'cluster of clues' into a three-dimensional model that revealed activity not previously detected.

    Research indicates that the Wilmington Fault is usually supposed to rupture every 3,200 to 4,700 years - however it has been dormant now for millions of years.

    There are fears for the communities of Los Angeles and Long Beach, which are built on the Wilmington Fault.

    'I hope bringing attention to it can potentially increase safety in the region,' study author Franklin Wolfe, a doctoral candidate who is part of Harvard's structural geology and Earth resources group, said at the time of publication.

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