All Types of Large Earthquakes Produce Prompt Gravity Signals

When major earthquakes occur, they displace enormous amounts of mass. This motion creates tiny perturbations in Earth’s gravitational field that travel at the speed of light—more than 4 orders of magnitude faster than the elastic seismic waves emanating from the same tremor. Because these prompt elastogravity signals (PEGS) precede seismic waves, the perturbations have the potential to improve early-warning systems by reducing the time it takes to estimate the size of large-magnitude earthquakes.

The weakness of these elastogravity waves, however, has made them extremely difficult to detect; the first PEGS observations weren’t published until 2016. Now Vallée and Juhel report multiple new observations of these signals from five earthquakes ranging in magnitude from 7.9 to 8.8, significantly smaller events than the magnitude 9.1 Tohoku earthquake from which their existence was first discovered.

The researchers identified these faint signals using a multistep approach. First, to better understand the conditions under which elastogravity waves are easiest to detect, the team developed a series of numerical simulations to evaluate how the depth and type of earthquake affect the signals’ expected amplitude. The results, which indicate that shallow strike-slip and deep events have a greater chance of being recorded than megathrust subduction zone earthquakes, helped inform the authors’ ensuing analysis of the records from large earthquakes that have occurred within the past 25 years.

This analysis revealed the presence of PEGS preceding seismic waves during several major earthquakes. These include the 2012 magnitude 8.6 Wharton Basin event, the largest strike-slip earthquake ever recorded, and two large and very deep tremors: the 2018 magnitude 8.2 Fiji earthquake and the 1994 magnitude 8.2 Bolivia event. By combining observations from several instruments, the team was also able to improve the signal-to-noise ratios enough to detect elastogravity waves from two additional tremors, including the 2018 magnitude 7.9 strike-slip event off Alaska.

The results show that the successful detection of PEGS is not restricted to exceptional (greater than magnitude 9) megathrust earthquakes. These findings indicate that PEGS observations have the potential to significantly improve the speed and reliability of early-warning systems in a lot of settings where the faster detection of major earthquakes could enhance rapid emergency response and/or improve tsunami hazard assessments.

2 Earthquakes Shake The Philippines; At Least 16 Dead

A powerful 6.4 earthquake struck the Philippines on Tuesday, the day after a different temblor took lives and collapsed buildings.

Rescuers continued to search for survivors from Monday’s quake, centered just 50 miles northwest of Manila, the capital. That quake killed at least 16 people, according to The Associated Press. So far, it appears that Tuesday’s 6.4 magnitude quake in Eastern Samar province did not cause any casualties or major damage.

Monday’s magnitude 6.1 quake struck Pampanga province, north of Manila, shortly after 5 p.m. local time. A supermarket collapsed in the municipality of Porac, killing at least five people, the AP reports. Others remain missing.

One man was reportedly pulled out alive from the supermarket’s rubble on Tuesday morning, to cheers from onlookers.

“We’re all very happy, many clapped their hands in relief because we’re still finding survivors after several hours,” Porac Councilor Maynard Lapid told the AP.

Fifteen of the dead were in Pampanga province, the state news service reported. Philippine President Rodrigo Duterte arrived in the affected area Tuesday, where he inspected the damage and was briefed on the situation.

Aurelia Daeng, 65, told Reuters that she was in her family’s drugstore when Monday’s quake struck. “It was very strong. It was our first time experiencing something like that,” she told the news service. “This one, it’s terrifying.”

Monday’s quake also shook the nation’s capital, where panicked office workers fled buildings, some in hard hats, according to Reuters.

More than 400 aftershocks continued to unsettle residents after Monday’s quake, and the government closed more than 1,600 schools in the region. Central Luzon, the area struck, is in one of the country’s most seismically active regions, home to three major faults and an oceanic trench.

Philippine seismologists said the two earthquakes were not related, the AP reports. The country is part of the “Ring of Fire,” a belt of heavy seismic activity where some 90 percent of the world’s earthquakes occur, according to the U.S. Geological Survey.

Strong Earthquake Strikes Philippines, Killing 11 People

MANILA — A powerful earthquake shook the northern Philippines on Monday, leaving at least 11 people dead in collapsed buildings, municipal and disaster relief officials said.

The Philippine Institute of Volcanology and Seismology said the quake had registered a magnitude of 6.1 and had been centered near the town of Castillejos in Zambales Province, west of Manila. It struck shortly after 5 p.m., as government offices and private businesses were closing for the day.

In the town of Porac, northwest of Manila, five people were reported crushed to death after a wall in a four-story supermarket collapsed, RJ Mago, a spokesman for the National Disaster Risk Reduction and Management Council, told a local radio station.

[One day after the deadly tremor, a powerful earthquake struck Samar, an island in the central eastern Philippines.]

He said an older woman and her granddaughter who had been injured at the supermarket had been taken to a hospital and were in good condition.

Lilia Pineda, the governor of the northern province of Pampanga, said that she had received reports that the quake had killed eight people there and had knocked out power.

“Almost all concrete electric posts in the villages of Lubao town have fallen down,” she said.

The quake was felt in varying intensities in Manila, where news outlets reported panicked workers fleeing tall office buildings. It was also intense in Malolos and Obando, north of the capital; in Lipa, a city south of Manila; and in the town of Magalang in Pampanga Province. At least 25 urban centers and provinces recorded tremors.

Renato U. Solidum Jr., an official at the Department of Science and Technology, said that although the quake had not caused extensive damage, it could produce many aftershocks.

“This earthquake is not a major earthquake, but it’s a strong earthquake,” he said, adding, “This is already far from Metro Manila but a little bit shallow so we can feel it.” Seventeen aftershocks were recorded by the state seismology institute.

Because of its location on the so-called Pacific Ring of Fire, the Philippines is prone to earthquakes and volcanic eruptions caused by the movement of tectonic plates.

In October 2013, nearly 100 people were killed after a powerful earthquake struck the central island of Bohol.

Volcano In Indonesia’s Bali Erupts, Triggering Rains Of Ashes

Mount Agung volcano in Bali resort Island of central Indonesia on Sunday spewed a column of ashes by up to two km onto the sky, leaving rains of ashes, a disaster agency official said.

Thousands of masks have been distributed to the communities amid the fears of the ashes impacting human respiratory, spokesman of national disaster management agency Sutopo Purwo Nugroho said.

The eruption occurred at 08:23 a.m. local time with belching of ash and smoke heading southwest of the crater, he said.

No halt of flight however took place at the I Gusti Ngurah Rai International Airport, said the official.

Rains of ashes with an intensity ranging from thin to thick have been pouring down in the districts of Karang Asem, Klungkung and Bangli, he added.

No report of casualty has so far been reached after the eruption, said Sutopo.

Mount Agung alert status’s remains at the second highest level with no-go zone at four km from the crater.

Mount Agung is situated in Karangasem district and about 70 km from tourist hub Kuta. In its last eruption in 1963, more than 1,100 people were killed.

State Of Emergency Declared As 3rd Day Of Severe Weather Outbreak Spawns Tornadoes In Eastern US

A string of violent storms that spawned possible tornadoes on Friday capped off a wild week of severe weather across the southern and eastern U.S.

Mississippi Gov. Phil Bryant declared a state of emergency on Friday in response to the tornadoes that left behind a trail of destruction on Thursday. This is the second time in less than a week that a state of emergency has been declared in Mississippi due to tornadoes.

As of Friday afternoon, at least five fatalities had been reported due to the storm. The latest fatality is from a traffic incident involving hydroplaning in Fort Gordon, Georgia, on Friday evening.

Earlier Friday morning, the storm caused the death of an 8-year-old girl in Leon County, Florida. The Leon County Sheriff’s Office report that a tree fell into a house in Woodville, located south of Tallahassee, killing the girl and injuring a 12-year-old boy.

Three deaths occurred on Thursday – one in Alabama and two in Mississippi.

A 42-year-old woman was killed Thursday night in St. Clair County, Alabama. Monica Clements died when a when a tree fell on her home, St. Clair County Sheriff’s Office told local news station WRBC. According to officials, Clements’ 10-year-old son was also home at the time of the incident. He sustained minor injuries.

In Mississippi, Amite County Coroner Campbell Sharp told local news station WLBT that 24-year-old Kenderick Magee was killed while driving in the severe weather. Magee’s car crashed on Bean Road in the Gillsburg Community. He died as a result of his injuries.

A tree fell onto a vehicle Thursday afternoon in Neshoba County, Mississippi, leaving one person dead, according to the Neshoba Democrat.

There have been widespread power outages as the storms blast eastward. Over 200,000 electric customers were without power on Friday evening from Mississippi to Florida and northward through Virginia, according to PowerOutage.us. North Carolina topped the list with over 70,000 outages. These numbers started to decline on Friday night.

Travel delays mounted as fallen trees and flooding made some roads impassable. Atlanta’s Hartsfield-Jackson International Airport had over 1,000 delays on Friday, and airline delays and cancellations will continue to have ripple effects for travelers across the nation.

Flash flood, severe thunderstorm and tornado warnings clashed in regions of Mississippi and Louisiana Thursday afternoon as a line of vigorous thunderstorms swept through the region. One tornado just missed striking Jackson, Mississippi, but instead passed through the nearby town of Clinton. Cars lay strewn across a Walmart parking lot, knocked over onto their sides while rain continued to fall.

In Utica, Mississippi, authorities reported a Hinds County school bus trapped by two trees on the road. Officials confirm that the driver and children are okay. According to officials, homes have been destroyed in Morton, Mississippi, after severe storms and a potential tornado moved through the area.

Storms ravaged Mississippi, Alabama and the Florida Panhandle before moving into western Georgia on Thursday night. Having seen the destruction that played out in the Mississippi Valley over the past few days, many school districts in central Georgia canceled class for Friday as part of storm preparation tactics.

The multi-day outbreak began on Wednesday afternoon when powerful thunderstorms developed from the Texas Panhandle to central Iowa. One tornado was confirmed near Higgins, Texas, Wednesday evening. Two EF0 tornadoes also struck Missouri, one near Greenfield and another near Meinert.

A rare phenomenon occurred on Wednesday as twin tornadoes – two tornadoes appearing near each other at the same time – touched down 4 miles west-northwest of Shattuck, Oklahoma.

Weather Officials Upgrade Hurricane Michael To Category 5 Storm As It Struck Florida

Scientists at NOAA’s National Hurricane Center announced on Friday that Hurricane Michael was a Category 5 hurricane on the Saffir-Simpson Hurricane Wind Scale when it made landfall near Mexico Beach, Florida on Oct. 10, 2018. It was previously listed as a Category 4 hurricane.

The adjustment to the hurricane’s category came after a post-storm analysis of the devastating storm that hit the Florida Panhandle last year. Scientists now estimate that the wind intensity at landfall was 160 mph, not the previously estimated 155 mph. The additional 5 mph was enough to push it into the next category.

“It will look like a bomb or a tsunami hit the area,” AccuWeather Founder and President Dr. Joel Myers said before the hurricane hit.

The now-Category 5 hurricane had blasted through the Florida Panhandle, carving a path of destruction through the East Coast before tracking back into the Atlantic. Before the storm hit, Myers estimated there would be about $30 billion in damage from the storm. The last Category 5 hurricane to strike the mainland U.S. was Hurricane Andrew in 1992, which was also initially designated as a Category 4 and was later upgraded to a Category 5.

“When looking at a hurricane at real time, you don’t have time to look at every piece of information,” AccuWeather Hurricane Expert Dan Kottlowski said. “When doing a post analysis, you can look at damage. The engineers go in and can see how much damage was done and how much wind it takes.”

Prior to becoming a Category 5, Michael was already known as one of the most destructive and powerful storms in recorded history.

Michael had a minimum central pressure of 27.13 inches of mercury when it made landfall, making it the third-most intense U.S. landfalling hurricane behind Katrina and Andrew.

“The minimum central pressure is probably the most accurate way to measure the intensity of a hurricane,” AccuWeather Senior Meteorologist Alex Sosnowski said.

Measuring the wind speed of a hurricane can often prove more difficult, as anemometers can be destroyed or blown away at wind speeds above 100 mph on land.

Some meteorologists stated back in October that they would not be surprised if it was later upgraded to a Category 5.

“Based on central pressure and looking at some of the damage photos and videos coming in, I would not be shocked if Michael is upgraded to a Category 5 hurricane after official review,” Sosnowski said a few days after Hurricane Michael hit.

But even with the damage at around $30 billion, the Category 5 storm didn’t come close to the financial losses of Hurricane Harvey, a Category 4 storm at landfall, which had an economic impact of $190 billion.

Kottlowski points out that even though Michael’s damage was catastrophic, the financial cost shows that the Category 5 hurricane missed highly populated areas.

“Opportunities will be there for these monstrous storms to develop,” Kottlowski said. “If we can do anything, it’s to get people to realize that you have to prepare.”

Data Mining Digs Up Hidden Clues To Major California Earthquake Triggers

A powerful computational study of southern California seismic records has revealed detailed information about a plethora of previously undetected small earthquakes, giving a more precise picture about stress in the earth’s crust. A new publicly available catalog of these findings will help seismologists better understand the stresses triggering the larger earthquakes that occasionally rock the region.

“It’s very difficult to unpack what triggers larger earthquakes because they are infrequent, but with this new information about a huge number of small earthquakes, we can see how stress evolves in fault systems,” said Daniel Trugman, a post-doctoral fellow at Los Alamos National Laboratory and coauthor of a paper published in the journal Science today. “This new information about triggering mechanisms and hidden foreshocks gives us a much better platform for explaining how big quakes get started,” Trugman said.

Crunching the Numbers

Trugman and coauthors from the California Institute of Technology and Scripps Institution of Oceanography performed a massive data mining operation of the Southern California Seismic Network for real quakes buried in the noise. The team was able to detect, understand, and locate quakes more precisely, and they created the most comprehensive earthquake catalog to date. The work identified 1.81 million quakes — 10 times more earthquakes occurring 10 times more frequently than quakes previously identified using traditional seismology methods.

The team developed a comprehensive, detailed earthquake library for the entire southern California region, called the Quake Template Matching (QTM) catalog. They are using it to create a more complete map of California earthquake faults and behavior. This catalog may help researchers detect and locate quakes more precisely.

The team analyzed nearly two decades of data collected by the Southern California Seismic Network. The network, considered one of the world’s best seismic systems, amasses a catalog of quakes from 550 seismic monitoring stations in the region. The SCSN catalog is based entirely on the traditional approach: manual observation and visual analysis. But Trugman says this traditional approach misses many weak signals that are indicators of small earthquakes.

Matching Templates Is Key

The team improved on this catalog with data mining. Using parallel computing, they crunched nearly 100 terabytes of data across 200 graphics processing units. Zooming in at high resolution for a 10-year period, they performed template matching using seismograms (waveforms or signals) of previously identified quakes. To create templates, they cut out pieces of waveforms from previously recorded earthquakes and matched those waveforms to patterns of signals recorded simultaneously from multiple seismic stations. Template matching has been done before, but never at this scale.

“Now we can automate it and search exhaustively through the full waveform archive to find signals of very small earthquakes previously hidden in the noise,” Trugman explained.

Applying the templates found events quake precursors, foreshocks and small quakes that had been missed with manual methods. Those events often provide key physical and geographic details to help predict big quakes. The team also identified initiation sequences that reveal how quakes are triggered.

New details also revealed three-dimensional geometry and fault structures, which will support development of more realistic models.

Recently, Trugman and Los Alamos colleagues have applied machine learning to study earthquakes created in laboratory quake machines. That works has uncovered important details about earthquake behavior that may be used to predict quakes.

“In the laboratory, we see small events as precursors to big slip events, but we don’t see this consistently in the real world. This big data template-matching analysis bridges the gap,” he said. “And now we’ve discovered quakes previously discounted as noise and learned more about their behavior. If we can identify these sequences as foreshocks in real time, we can predict the big one.”