Tag Archives: earthquake

Massive earthquake hits Pakistan: At least 209 dead, scores injured

KARACHI: At least 209 people lost their lives and hundreds others sustained injuries in structures’ collapse and landslides caused by a powerful 7.5 magnitude earthquake that jolted northern parts of Pakistan on Monday.

The enormity of the quake can be gauged from the fact that the tremors were felt alls across South Asia.

Majority of deaths were reported from Shangla while the death toll is feared to rise even further in view of the massiveness of this natural calamity.

The powerful quake caused a large number of walls, houses and other structures to cave in while many instances of land-sliding were also reported from some parts of the affected areas.

The earthquake was also felt in several parts of Punjab including Lahore where thousands of people had to rush outside of their houses, shops, offices and other structures for safety. They said ‘never before an earthquake had made us feel this much panic’.

Tremors were also felt in Islamabad, Sargodha, Kashmir and several other parts of the country.

According to Commissioner Malakand, 137 people died in Swat-Malakand division while 835 suffered injuries. He said as many as 813 houses collapsed in Malakand.

Chief Minister Gilgit-Baltistan said the intenstity of today’s earthquake seemd much greater compared to that of 2005.

The US Geological Survey put the epicentre near Jurm in northeast Afghanistan, 250 kilometres (160 miles) from the capital Kabul and at a depth of 213.5 kilometres.

The Met Office in Pakistan said the magnitude was 8.1 on the Richter scale.

The epicentre is just a few hundred kilometres from the site of a 7.6 magnitude quake that struck in October 2005, killing more than 75,000 people and displacing some 3.5 million more.

The earthquake was said to be one of the most powerful ever recorded in Pakistan’s history.

Quake in Afghanistan and India

Thousands of frightened people rushed into the streets across Afghanistan and India as the quake rocked a swathe of the subcontinent. Shockwaves were felt in areas as far away as New Delhi in India and Kabul in Afghanistan.

Hundreds of people raced from buildings onto the streets in different cities while the quake was also felt in the Kashmir region.

Source: The News 

This map of Turkey shows the artists' interpretation of the North Anatolian Fault (blue line) and the possible site of an earthquake (white lines) that could strike beneath the Sea of Marmara.

Image: NASA, and Christine Daniloff and Jose-Luis Olivares/MIT

Groundwater composition as potential precursor to earthquakes

By Meres J. Weche


 

The world experiences over 13,000 earthquakes per year reaching a Richter magnitude of 4.0 or greater. But what if there was a way to predict these oft-deadly earthquakes and, through a reliable process, mitigate loss of life and damage to vital urban infrastructures?

Earthquake prediction is the “holy grail” of geophysics, says KAUST’s Dr. Sigurjón Jónsson, Associate Professor of Earth Science and Engineering and Principal Investigator of the Crustal Deformation and InSAR Group. But after some initial optimism among scientists in the 1970′s about the reality of predicting earthquakes, ushered in by the successful prediction within hours of a major earthquake in China in 1975, several failed predictions have since then moved the pendulum towards skepticism from the 1990′s onwards.

This map of Turkey shows the artists' interpretation of the North Anatolian Fault (blue line) and the possible site of an earthquake (white lines) that could strike beneath the Sea of Marmara. Image: NASA, and Christine Daniloff and Jose-Luis Olivares/MIT
This map of Turkey shows the artists’ interpretation of the North Anatolian Fault (blue line) and the possible site of an earthquake (white lines) that could strike beneath the Sea of Marmara.
Image: NASA, and Christine Daniloff and Jose-Luis Olivares/MIT

In a study recently published in Nature Geoscience by a group of Icelandic and Swedish researchers, including Prof. Sigurjón Jónsson, an interesting correlation was established between two earthquakes greater than magnitude 5 in North Iceland, in 2012 and 2013, and the observed changing chemical composition of area groundwater prior to these tectonic events. The changes included variations in dissolved element concentrations and fluctuations in the proportion of stable isotopes of oxygen and hydrogen.

Can We Really Predict Earthquakes?

The basic common denominator guiding scientists and general observers investigating the predictability of earthquakes is the detection of these noticeable changes before seismic events. Some of these observable precursors are changes in groundwater level, radon gas sometimes coming out from the ground, smaller quakes called foreshocks, and even strange behavior by some animals before large earthquakes.

There are essentially three prevailing schools of thought in earthquake prediction among scientists. There’s a first group of scientists who believe that earthquake prediction is achievable but we simply don’t yet know how to do it reliably. They believe that we may, at some point in the future, be able to give short-term predictions.

Then there’s another class of scientists who believe that we will never be able to predict earthquakes. Their philosophy is that the exact start of earthquakes is simply randomly occurring and that the best thing we can do is to retrofit our houses and make probability forecasts — but no short-term warnings.

The last group, which currently represents a minority of scientists who are not often taken seriously, believes that earthquakes are indeed predictable and that we have the tools to do it.

Following the wave of optimism in the ’70s and ’80s, the interest and confidence of scientists in predicting earthquakes have generally subsided, along with the funding. Scientists now tend to focus mainly on understanding the physics behind earthquakes. As Prof. Jónsson summarizes:

“From geology and from earthquake occurrence today we can more or less see where in the world we have large earthquakes and where we have areas which are relatively safe. Although we cannot make short-term predictions we can make what we call forecasts. We can give probabilities. But short-term predictions are not achievable and may never be. We will see.”

The Message from the Earth’s Cracking Crust

Iceland was an ideal location to conduct the collaborative study undertaken by the scientists from Akureyri University, the University of Iceland, Landsvirkjun (the National Power Company of Iceland), the University of Stockholm, the University of Gothenburg and Karolinska Institutet in Stockholm, and KAUST.

“Iceland is a good testing ground because, geologically speaking, it’s very active. It has erupting volcanoes and it has large earthquakes also happening relatively often compared to many other places. And these areas that are active are relatively accessible,” said Prof. Jónsson.

The team of researchers monitored the chemistry, temperature and pressure in a few water wells in north Iceland for a period of five years more or less continuously. “They have been doing this to form an understanding of the variability of these chemical compounds in the wells; and then possibly associate significant changes to tectonic or major events,” he adds.

Through the five-year data collection period, which began in 2008, they were able to detect perceptible changes in the aquifer system as much as four to six months prior to the two recorded earthquakes: one of a magnitude 5.6 in October 2012 and a second one of magnitude 5.5 in April 2013. Their main observation was that the proportion of young local precipitation water in the geothermal water increased – in proportion to water that fell as rain thousands of years ago (aquifer systems are typically a mix of these two). At the same time, alterations were evident in the dissolved chemicals like sodium, calcium and silicon during that precursor period. Interestingly, the proportion went back to its previous state about three months after the quakes.

While the scientists are cautioning that this is not a confirmation that earthquake predictions are now feasible, the observations are promising and worthy of further investigation involving more exhaustive monitoring in additional locations. But, statistically speaking, it would be very difficult to disassociate these changes in the groundwater chemical composition from the two earthquakes.

The reason why a change in the ratio between old and new water in the aquifer system is important is because it points to the development of small fractures from the build-up of stress on the rocks before an earthquake. So the new rainwater seeps through the newly formed cracks, or microfracturing, in the rocky soil. Prof. Sigurjón Jónsson illustrates this as follows:

“It’s similar to when you take a piece of wood and you start to bend it. At some point before it snaps it starts to crack a little; and then poof it snaps. Something similar might be happening in the earth. Meaning that just before an earthquake happens, if you start to have a lot of micro-fracturing you will have water having an easier time to move around in the rocks.”

The team will be presenting their findings at the American Geophysical Union (AGU) meeting in San Francisco in December 2014. “It will be interesting to see the reaction there,” said Prof. Jónsson

Source: KAUST News

Seismic gap may be filled by an earthquake near Istanbul

After tracking seismic shifts, researchers say a major quake may occur off the coast of Istanbul.

Jennifer Chu 

When a segment of a major fault line goes quiet, it can mean one of two things: The “seismic gap” may simply be inactive — the result of two tectonic plates placidly gliding past each other — or the segment may be a source of potential earthquakes, quietly building tension over decades until an inevitable seismic release.

This map of Turkey shows the artists' interpretation of the North Anatolian Fault (blue line) and the possible site of an earthquake (white lines) that could strike beneath the Sea of Marmara. Image: NASA, and Christine Daniloff and Jose-Luis Olivares/MIT
This map of Turkey shows the artists’ interpretation of the North Anatolian Fault (blue line) and the possible site of an earthquake (white lines) that could strike beneath the Sea of Marmara.
Image: NASA, and Christine Daniloff and Jose-Luis Olivares/MIT

Researchers from MIT and Turkey have found evidence for both types of behavior on different segments of the North Anatolian Fault — one of the most energetic earthquake zones in the world. The fault, similar in scale to California’s San Andreas Fault, stretches for about 745 miles across northern Turkey and into the Aegean Sea.

The researchers analyzed 20 years of GPS data along the fault, and determined that the next large earthquake to strike the region will likely occur along a seismic gap beneath the Sea of Marmara, some five miles west of Istanbul. In contrast, the western segment of the seismic gap appears to be moving without producing large earthquakes.

“Istanbul is a large city, and many of the buildings are very old and not built to the highest modern standards compared to, say, southern California,” says Michael Floyd, a research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “From an earthquake scientist’s perspective, this is a hotspot for potential seismic hazards.”

Although it’s impossible to pinpoint when such a quake might occur, Floyd says this one could be powerful — on the order of a magnitude 7 temblor, or stronger.

“When people talk about when the next quake will be, what they’re really asking is, ‘When will it be, to within a few hours, so that I can evacuate?’ But earthquakes can’t be predicted that way,” Floyd says. “Ultimately, for people’s safety, we encourage them to be prepared. To be prepared, they need to know what to prepare for — that’s where our work can contribute”

Floyd and his colleagues, including Semih Ergintav of the Kandilli Observatory and Earthquake Research Institute in Istanbul and MIT research scientist Robert Reilinger, have published their seismic analysis in the journal Geophysical Research Letters.

In recent decades, major earthquakes have occurred along the North Anatolian Fault in a roughly domino-like fashion, breaking sequentially from east to west. The most recent quake occurred in 1999 in the city of Izmit, just east of Istanbul. The initial shock, which lasted less than a minute, killed thousands. As Istanbul sits at the fault’s western end, many scientists have thought the city will be near the epicenter of the next major quake.

To get an idea of exactly where the fault may fracture next, the MIT and Turkish researchers used GPS data to measure the region’s ground movement over the last 20 years. The group took data along the fault from about 100 GPS locations, including stations where data are collected continuously and sites where instruments are episodically set up over small markers on the ground, the positions of which can be recorded over time as the Earth slowly shifts.

“By continuously tracking, we can tell which parts of the Earth’s crust are moving relative to other parts, and we can see that this fault has relative motion across it at about the rate at which your fingernail grows,” Floyd says.

From their ground data, the researchers estimate that, for the most part, the North Anatolian Fault must move at about 25 millimeters — or one inch — per year, sliding quietly or slipping in a series of earthquakes.

As there’s currently no way to track the Earth’s movement offshore, the group also used fault models to estimate the motion off the Turkish coast. The team identified a segment of the fault under the Sea of Marmara, west of Istanbul, that is essentially stuck, with the “missing” slip accumulating at 10 to 15 millimeters per year. This section — called the Princes’ Island segment, for a nearby tourist destination — last experienced an earthquake 250 years ago.

Floyd and colleagues calculate that the Princes’ Island segment should have slipped about 8 to 11 feet — but it hasn’t. Instead, strain has likely been building along the segment for the last 250 years. If this tension were to break the fault in one cataclysmic earthquake, the Earth could shift by as much as 11 feet within seconds.

That gives very little warning for nearby Istanbul, says Marco Bohnhoff, a professor at the German Research Center for Geosciences in Potsdam, Germany.

“The nucleation point is pretty close to the city center, which makes early warning time pretty short — between two to six seconds,” says Bohnhoff, who has studied seismic patterns in the region. “Since the international airport is located in an area where ground motion would be high, it would be difficult to get in emergency troops, and unfortunately 90 percent of buildings in Istanbul do not fulfill building codes, and might not resist the expected earthquake.”

Although such accumulated strain may be released in a series of smaller, less hazardous rumbles, Floyd says that given the historical pattern of major quakes along the North Anatolian Fault, it would be reasonable to expect a large earthquake off the coast of Istanbul within the next few decades.

“Earthquakes are not regular or predictable,” Floyd says. “They’re far more random over the long run, and you can go many lifetimes without experiencing one. But it only takes one to affect many lives. In a location like Istanbul that is known to be subject to large earthquakes, it comes back to the message: Always be prepared.”

Source: MIT News Office