Comment: The Pacific Tsunami Warning Center (PTWC) issued an updated situation report, saying that "Tsunami waves reaching more than 3 meters above the tide level are possible along some coasts of Mexico," and waves reaching up to one meter are expected to hit the coastlines of adjacent countries.


UPDATES: 09.35 (CET)

Officials said that it was the strongest quake to hit the capital since the 1985 tremor that killed thousands and flattened swathes of Mexico City. Five people have been killed including two children in Tabasco state. A deep 6.1 magnitude earthquake hit off Japan's Bonin Islands yesterday at a depth of 450 kilometres (280 miles).

An eyewitness uploaded dazzling footage of earthquake lights that appeared in the skies over Mexico City shortly after the quake.


The Pacific Tsunami Warning Center says waves of 1 metre (3.3 feet) above the tide level were measured off Salina Cruz. Smaller tsunami waves were observed on the coast or measured by ocean gauges in several other places.

The center's forecast said Ecuador, El Salvador and Guatemala could see waves of a metre or less. No threat was posed to Hawaii and the western and South Pacific.

16.00 (CET)

The death toll from the 8.2 magnitude (registered by local calculations) earthquake that hit Mexico has reached at least 32, according to tallies from local authorities. "It was a major earthquake in scale and magnitude, the strongest in the past 100 years," President Peña Nieto said. The US Geological Survey reported the quake's magnitude at 8.1.

Peña Nieto said the quake was felt by 50 million of the country's 120 million residents, and was also felt in much of Guatemala, which borders Chiapas. He warned more aftershocks are likely, and has urged people to check their homes and offices for structural damage and gas leaks.


Sept. 9 (09.55 CET)

The death toll from yesterday's Mexico earthquake, the strongest earthquake to hit the country in a century, is at least 61. Jana Pursely, a geophysicist at the US Geological Survey, told CNN that the quake was relatively shallow, which resulted in more "intense shaking".

Scenes of demolished buildings, teetering streetlight posts, and blacked-out subway stations have been circulating on social media. Mexico's Federal Commission of Electricity calculates that 1.85 million residents across the country were affected by power cuts.


The region where the earthquake struck is one of the most active seismic zones in the country: this is where the Cocos Plate dives, or subducts, under the North American plate. "Earthquakes of this size are not uncommon at subduction zone boundaries," notes Jascha Polet, a seismologist at California Polytechnic State University in Pomona.

But this quake was different: it occurred within the Cocos plate, as it warped or bent, not at the boundary with the North American plate, according to the US Geological Survey.

"The type of faulting that occurred here does not usually produce earthquakes of this magnitude," says Polet. "There have been others in the past 50 years of similar type and location, but none that was even close to this size." It is still too early to say why the earthquake was so massive, she adds, but "it is sure to inspire much future research".

Mexico's seismology agency has registered at least 337 aftershocks, with the strongest reaching a magnitude of 6.1.


Meanwhile Hurricane Katia has made landfall in the state of Veracruz on the Mexican Gulf coast, the U.S. National Hurricane Center (NHC) said. It lost some strength before it landed about 115 miles (185 km) northwest of the port city of Veracruz as a Category 1 storm with sustained winds 75 mph (120 km/h). The storm was expected to weaken rapidly over the next day, the NHC said.

Update (Sept. 12)

The death toll from last week's powerful earthquake in Mexico has risen to at least 96. Authorities also say 2.5 million people are in need of food, water and electricity. The 8.1-magnitude quake struck Friday near Mexico's border with Guatemala. It damaged at least 12,000 homes, and that number is expected to rise.


According to Science Magazine last week's unusual temblor may have relieved pressure in one of two "seismic gaps" in the subduction zone off Mexico's coast, where tectonic plates grind past one another. The epicenter of the quake, which struck just before midnight local time, was just southeast of the Tehuantepec gap, a 125-kilometer-long stretch of Mexico's Pacific coast that has been seismically silent since record-keeping began more than a century ago.

All along that coast, the ocean's tectonic plates meet the continental North American plate and are forced underneath it. Violent earthquakes mark the release of built-up pressure between the grinding plates. But the ruptures have somehow avoided the Tehuantepec gap and the Guerrero gap, more than 500 kilometers to the northwest.

For decades, scientists have monitored the Guerrero gap because of its proximity to Mexico City. A rupture there could devastate the capital, which is built on a drained lakebed that amplifies seismic waves. In 1985, a magnitude-8.1 quake near the Guerrero gap killed thousands, spurring the city to install a seismic alert system and tighten building codes. Those measures seemed to help last week: The capital sustained little damage in spite of considerable shaking.

The quake's effect on the gap is hard to judge though, because of its unusual origin. Most big Mexican earthquakes occur right along the interface between the colliding Cocos and North American plates. But this rupture began 70 kilometers down, within the Cocos plate itself, and rose up before stopping at about 40 kilometers' depth, likely at the plate interface.

"It's not the same fault that they're expecting [to close] the Tehuantepec gap," says Joann Stock, a seismologist at the California Institute of Technology in Pasadena.

That leaves the future risk of the Tehuantepec gap unclear. In fact, Stock says, last week's quake might have even added stress at the gap and increased chances for future slipping. But, she adds, the depth of the shaking had at least one benefit: The rupture didn't break through all the way to the ocean floor, which dampened tsunamis. The resulting waves in Chiapas and Oaxaca were only 2 to 3 meters high.

Vladimir Kostoglodov, a seismologist at UNAM in Mexico City, says he is fielding requests for data from researchers around the world who want to investigate this "extremely strange" earthquake and its aftermath. "It's worth making a big effort to learn what's happening," he says. "This might happen in other subduction zones in other parts of the world."

Comment: September so far has been an almost apocalyptic month of environmental events