Magnitude 7.3 Quake Hits Laiwui, Indonesia, No Tsunami

A 7.3-magnitude earthquake has jolted South Halmahera regency in North Maluku. According to the United States Geological Survey (USGS), the quake occurred at 4:10 p.m. Jakarta time or 6:10 p.m. local time, 102 kilometers north-northeast of Laiwui in South Halmahera, at a depth of 10 kilometers.

The Meteorology, Climatology and Geophysics Agency (BMKG) said there was no tsunami potential detected because of the earthquake. It has also recorded several aftershocks. Meanwhile, the BMKG reported at 5:04 p.m. Jakarta time, there was a 5.2-magnitude earthquake with an epicenter at 61 kilometers southwestern off Biak Numfor regency in Papua.

Based on official information from the South Halmahera Disaster Mitigation Agency (BPBD), the quake was mostly felt in the regency for two to five seconds, prompting people to panic and rush out of their homes.

 

Tsunami Threat Expires Following 6.9-Magnitude Earthquake In Indonesia

A powerful earthquake struck under the water surrounding Indonesia, prompting a tsunami warning which encompasses hundreds of the country’s 17,000 islands.

Indonesian officials issued the tsunami warning for coastal areas after the earthquake occurred in the Molucca Sea, which is located between the islands of Sulawesi and Maluku. The warning has since expired and there is no tsunami threat at this time.

The United States Geological Survey stated that the earthquake had a magnitude of 6.9, while officials from Indonesia stated that the earthquake was slightly stronger with a magnitude of 7.1.

The tsunami warning was in effect for the eastern coast of North Sulawesi and the western coast of North Maluku. Latest projections are for a tsunami of 0.5 of a meter (1.5 feet) or less.

The earthquake rumbled at 10:08 p.m. local time (11:08 a.m. EDT) on Sunday.

There is potential for heavy-intensity rainfall with lightning, thunder, and gusty winds until 3:30 a.m. local time (WIB).

The earthquake caused panic in the city of Ternate on the island chain of Maluku.

“Showers and thunderstorms will continue to be around central Indonesia through Monday,” according to AccuWeather Meteorologist Maura Kelly.

7,1 Magnitude Earthquake Hits Near Ridgecrest In Southern California

A 7.1-magnitude earthquake rocked Southern California on Friday night — the second temblor to hit near Ridgecrest in less than two days.

The latest earthquake occurred 11 miles northeast of Ridgecrest, according to the US Geological Survey. It rocked buildings and cracked foundations, sending jittery residents out on the streets.

It comes a day after a 6.4-magnitude earthquake centered near Ridgecrest rattled the state Thursday. That earthquake has produced more than 1,400 aftershocks, scientists said.

Multiple fires and injuries have been reported in Ridgecrest — about 150 miles from Los Angeles — after Friday’s earthquake, Kern County spokeswoman Megan Person said. The county has activated an emergency operations center, the fire department tweeted.

The San Bernardino County Fire Department said it has received multiple reports of damage from northwest communities in the county.

“Homes shifted, foundation cracks, retaining walls down,” the department said. “One injury (minor) with firefighters treating patient.”

Localized power outages in LA

In central Los Angeles, Friday’s earthquake felt stronger than the one a day earlier, making buildings rock back and forth forcefully. Donald Castle, who lives in Porterville west of Ridgecrest, said his house shook for between 20 and 25 seconds.

“It was more of a shake than what we had on the Fourth. It lasted longer and was more rolling,” he said.

Public safety units are being deployed throughout the city ” to ensure safety and inspect infrastructure,” Los Angeles Mayor Eric Garcetti said.

The Los Angeles Fire Department said there were reports of wires down and localized power outages in some parts of the city. Fire crews are still surveying the city, it said, but no major damage to infrastructure has been identified so far.

The fire department is no longer in Earthquake mode and has determined there are no injuries or significant damage in Los Angeles city, chief Ralph M. Terrazas tweeted.

The shaking was felt in Mexico and Las Vegas

The shaking was felt as far as Mexico, according to the USGS website.

The NBA Summer League game between the New Orleans Pelicans and the New York Knicks in Las Vegas was postponed Friday following reports of the quake. Scoreboards and speakers near the ceiling of the arena shook when the earthquake hit.

Quakes are part of an ongoing system

CalTech seismologist Lucy Jones said Friday both earthquakes are part of an ongoing sequence, of a “very energetic system.”

The latest 7.1 earthquake was the mainshock, while Thursday’s 6.4 magnitude shake was a foreshock, according to Jones. She said Friday’s earthquake was 10 times stronger than the one a day prior.

The 7.1 magnitude shake was five times bigger than Thursday’s, but released 11 times the amount of energy than the 6.4 shake, CNN Meteorologist Brandon Miller said.
Officials are not ruling out that there could be more earthquakes coming.

California Gov. Gavin Newsom said he has activated the state emergency operation center to its highest level.

“The state is coordinating mutual aid to local first responders,” he tweeted Friday night.

Magnitude 6.4 Earthquake Rattles Southern California

A magnitude 6.4 earthquake rattled a large swath of Southern California on Thursday morning, according to USGS.

There are no immediate reports of damages or injuries.

The quake hit at 10:33 a.m. near the town of Ridgecrest.

It was originally recorded as a 6.6 magnitude earthquake.

The quake was felt in Bakersfield minutes after it struck. People from the desert to the Pacific coast in Southern California reported feeling it.

Study Reveals Key Factor In Himalayan Earthquake Rupture

The Himalayan orogenic belt produces frequent large earthquakes that impact population centers for a distance of over 2500 km. In the central region, the 2015 Gorkha earthquake in Nepal, with moment magnitude (MW) 7.8, partially ruptured a ~120-km by 80-km patch of the Main Himalayan Thrust (MHT), the detachment that separates the underthrusting Indian plate from the overriding Himalayan orogeny.

The rupture highlights important scientific questions about Himalayan formation and seismic hazards. These questions include how to distinguish between different possible geometries of the MHT, and how to better define the structural causes and locations of rupture segmentation both across-strike and along-strike in the orogenic belt.

A study led by Prof. BAI Ling from the Institute of Tibetan Plateau Research (ITP) of the Chinese Academy of Sciences revealed that the rupture length of the 2015 MW 7.8 Gorkha earthquake was likely controlled by spatial (both along- and across-strike) variations in the Main Himalayan Thrust.

The researchers combined seismic waveforms from several different deployments, including 22 seismic stations ITP had deployed along the China-Nepal border with an average elevation of 4.5 km prior to the earthquake. Using arrival times and waveform modeling, they determined source parameters of earthquakes, velocity structures and discontinuity topography in and around the source area.

The study showed that the MHT exhibited clear lateral variation along the geologic strike, with the Lesser Himalayan ramp having moderate dip on the MHT beneath the mainshock area, and a flatter and deeper MHT beneath the eastern end of the aftershock zone.

Following these observations, the impetus now is to image the entire 2,500-km Himalayan front to determine the morphology of the MHT and the likely controls on the maximum magnitude of rupture that can be accommodated in different parts of this convergence zone.

The study, entitled “Lateral variation of the Main Himalayan Thrust controls the rupture length of the 2015 Gorkha earthquake in Nepal,” was published in Science Advances.

Tsunamis Warning Lifted In Japanese Coastal Regions After Earthquake

Japan’s meteorological agency has lifted an earlier tsunami warning, after a 6.8 magnitude earthquake was recorded at 10:22 p.m. Tuesday (9:22 a.m. ET) off the coast of Yamagata Prefecture in the north of the country.

The agency had originally warned that tsunamis were “expected to arrive imminently” in the coastal areas of Yamagata, Niigata and Ishikawa, with an advisory issued for four coastal regions.

The meteorological agency has advised residents to evacuate those coastal regions immediately and to not enter the sea or approach the coastal regions until the advisory has been lifted.

Slight sea-level changes may be observed in coastal regions, but no tsunami damage is expected, it added.

In March 2011, Japan was hit by a 9.0 magnitude earthquake, its worst ever. The massive quake rocked the country and triggered an enormous tsunami that resulted in the country’s worst nuclear disaster.

The earthquake was so strong that it permanently moved Japan’s main island, Honshu, more than two meters to the east. Its impact also raised huge waves up to 40 meters (approximately 131 feet) high that, as people were still reeling from the aftershocks, began crashing into the coast.

In Fukushima, approximately 256 kilometers (159 miles) north of Toyko, three reactors at the Fukushima Daiichi nuclear plant melted down, releasing radioactive materials into the air.

Nearly 20,000 people died in the earthquake and subsequent tsunami and nuclear meltdown, with more than 100,000 people evacuated from the area.

Big Earthquakes Might Make Sea Level Rise Worse

A GEOLOGIC ONE-TWO punch rocked the South Pacific in September 2009, as a magnitude 8.1 earthquake struck off the coast of the island nation of Samoa, followed mere moments later by a similarly intense temblor. A towering tsunami soon crashed onto the shores of islands nearby, leaving more than 180 dead and communities in ruins in Samoa, the neighboring U.S. territory of American Samoa, and surrounding islands.

But a new study, published in the Journal of Geophysical Research: Solid Earth, reveals that the quakes also sparked a slow-burning danger for the more than 55,000 residents of American Samoa: sea level rise that is five times as fast as the global average.

Like other island and coastal regions around the world, Samoa and American Samoa are facing encroaching waters as our warming world sends sea levels soaring at accelerating rates. In the wake of the mega-quakes, though, the researchers discovered that these Pacific islands are also sinking. The situation is particularly concerning for American Samoa, where the team estimates that, over the next 50 to a hundred years, local sea levels could rise by roughly a foot in addition to the anticipated effects of climate change.

While the contributions of big earthquakes won’t be the same everywhere, the discovery emphasizes the sometimes overlooked effects that geology can have on the increasing number of people around the world who call coastlines home. (Also find out how powerful quakes are priming the region around Mount Everest for a huge disaster.)

“Everybody is talking about climate change issues … but they overlooked the impact of the earthquake and associated land subsidence,” says study leader Shin-Chan Han of the University of Newcastle, Australia, referring to documents from regional governments on sea level rise.

“This is a really important thing to point out,” says geophysicist Laura Wallace of the geoscience consultancy firm GNS Science, Te Pū Ao, in New Zealand, who was not involved in the study. “It obviously has a big impact on the relative sea level changes people are going to see in places like [the Samoan islands].”

Geologic geometry

Plate tectonics is constantly reshaping the surface of our planet—a role particularly evident during an earthquake. Generally speaking, these events occur where tectonic plates are colliding or sliding against each other, building up geologic stress. When that pent-up energy is released suddenly, it can send blocks of the planet’s crust careening out of place. (Find out how smaller “hidden” earthquakes are affecting California.)

But not all the change from a big earthquake is immediate. Unlike the rigid crust, the rocks of the mantle below flow like cold molasses and gradually adjust to the sudden surface jolt, Wallace says. This can cause either sinking or uplift of the land that can continue for decades after a temblor strikes.

This prolonged landscape deformation is what intrigues Han. For years, he’s scoured data from the Gravity Recovery and Climate Experiment, or GRACE, satellites to hunt for the rise and fall of land after a quake. This satellite duo orbited Earth in a line from 2002 to 2017 and precisely tracked the gap between the spacecraft. As they passed over zones with slightly more mass, and thus stronger gravity, the leading craft would feel the tug just before the trailing one. This tweaked the space in between and registered as a wobble in the planet’s gravitational field that can reveal changes in the landmass below.

In the case of the 2009 earthquake, such changes were minute on a day-to-day basis. But eventually, the effects were large enough that Han saw something strange happening in the Samoan islands while poring over the GRACE data.

A rare coincidence

The 2009 event was a particularly unusual earthquake that initially baffled scientists, since the pair of powerful temblors ripped through the Earth nearly at the same time. One broke along a so-called normal fault, created due to the flex of the oceanic crust as it plunges under another tectonic plate in what’s known as a subduction zone. Another quake broke within the subduction zone due to the compressive forces of the colliding plates.

The researchers investigated the lingering impacts of these quakes using a combination of GRACE data and local GPS and tide gauge records. They then built a computer model to tease apart the complex interplay between the temblors and what is happening at the surface.

This data showed slow sinking of the landscape, driven primarily by the normal-fault quake. This particular earthquake causes one side of the landscape to fall in relation to the other, which sent the nearby islands sinking downward.

The team found that nearly a decade after the event, the island of Samoa has sunk by roughly 0.4 inches a year. The situation is particularly acute for American Samoa, which has seen more than 0.6 inches of subsidence each year, and it doesn’t look like it’s stopping anytime soon.

The pace outstrips the estimated rate of global sea level rise, which is creeping upward at some 0.13 inches a year. Flooding and seawater intrusion in freshwater aquifers are already grave concerns for residents of American Samoa, Han says, and the latest find only adds to the worry.

Bathtub oceans

This latest study emphasizes the need for greater awareness and continued monitoring to mitigate the potential effects of mega-quakes, Wallace says. However, predicting such sea level effects before an earthquake strikes is not feasible, since earthquake prediction itself remains elusive.

“This might be a problem that suddenly causes you heartburn next week,” Freymueller says, “or it might not cause any problem for the next century.”

This latest study emphasizes the need for greater awareness and continued monitoring to mitigate the potential effects of mega-quakes, Wallace says. However, predicting such sea level effects before an earthquake strikes is not feasible, since earthquake prediction itself remains elusive.

“This might be a problem that suddenly causes you heartburn next week,” Freymueller says, “or it might not cause any problem for the next century.”