Do you know that you have a treasure trove in your pocket? Well, most of you at least, except for the very few who do not carry a smartphone. The blogger is not talking about some treasure for questionable marketing purposes, where unknown cyberforces use your smartphone to secretly spy on your whereabouts or shopping habits. No, we are talking about a treasure trove for science. Remember the old days of desktop computers, when you were asked to participate in citizen science projects? You left the desktop connected to the web overnight and scientist used its meager computing power to calculate the number "pi" to 34 billion decimals or to help sift through signals from outer space looking for alien civilizations.
Today's smartphones not only have orders of magnitude more computing prowess than the desktops of yesteryear, they also have built-in sensors. These little devices can measure temperature, minute changes in magnetic fields, detect the tilt angle of a phone or the level of light reaching its screen. All phones are also equipped with accelerometers, which are tiny devices which can sense the movement of the phone in three dimensions. Pedometers for instance, apps which measure every step of yours, make use of them.
|A screen shot from Berkeley's My Shake App shows the readings from the accelerometer built into a smartphone.|
Now switch to earthquake science: You will be hard pressed to find any seismologist who does not want to install more instruments to monitor earthquakes. Today we have almost 500 such devices installed all over Northern California. But more would be better to improve the precision of earthquake locations, the imaging of faults, the understanding of the rhythm of plate movement and - most importantly - to get reliable early warning for earthquakes.
And what does all this have to do with the treasure trove? There are currently about 25 million smartphones registered in California, that means there are 25 million accelerometers available to measure ground shaking all over the State. No seismologist would even consider building a standard seismic network of that size. But if you could somehow tap into only a fraction of those smartphone accelerometers, you could create a seismic network larger than you might imagine in your wildest dreams.
Scientists at our Berkeley Seismological Lab and engineers at the Silicon Valley Innovation Labs of Deutsche Telekom have done exactly that: They have developed an app called "My Shake". It uses the measurements of the accelerometer in your Android smartphone to detect earthquakes. The big problem, of course, is to distinguish between the shaking due to the relatively rare earthquakes and all the other movement your smartphone is exposed to: You walk around or go jogging, you drive on BART, you go dancing at night. All of these activities excite the accelerometer more than any earthquake would do. However, through clever and complex programming the BSL researchers were able to discriminate between the various signals and concentrate on seismic ground shaking.
When running the app, the phones are connected to a central server computer which is programed to compare the recordings of the various accelerometers. Once enough of them show ground shaking signals, an earthquake is detected. In the future scientists hope to feed this information into the Earthquake Early Warning System (EEW) currently under development along the US West Coast. Also, such smartphone networks may even be programmed to be stand-alone EEW systems in areas with too few seismometers, like in Africa.
And what do you as the smart phone owner get, when you run My Shake? You will get live information about current earthquakes, live readings from the accelerometer in your phone (see picture), safety tips on how to act during an earthquake - and of course you get the satisfaction of being part of a citizen science project helping us to improve earthquake monitoring and early warning.
You can download the My Shake app in Google's Play Store by clicking here.
More general information about My Shake can be found at:
|A singularity of destruction in a sea of normalcy: The collapsed Weiguan Jinlong residential building in Tainan after the 6.4 earthquake. (Photo: Taipei Times)|
Pictures showing the destruction after a devastating temblor are never pretty. But the latest aerial photos coming out of the earthquake-struck city of Tainan in southern Taiwan are outright surreal. As far as the wide angle lens of the camera can see, the pictures show buildings which look undamaged and pristine. Only in the photo's center do two colossal grey apartment towers lie on their sides - keeled over as if they were felled like trees cut with a chainsaw. Rescue teams are still frantically searching for survivors. As of this writing more than one hundred people have been pulled out alive but more than 150 others are still missing, presumably trapped deep inside the fallen residential towers. The bodies of 13 residents who perished in the collapse have also been recovered.
To a seismologist's eye, however, this picture shows more than a surreal scene after one of nature's most devastating forces has struck. Why is it, one has to ask, that hundreds of buildings in Tainan's Yongkang District are intact while the twin 17-story towers of the Weiguan Jinlong residential building were left lying on their sides on Yongda Road when the shaking stopped? The earthquake itself, which occurred on Saturday shortly before 4:00 am (local time), had a magnitude of 6.4 and hence was only slightly larger than M=6.0 the South Napa earthquake of August 24, 2014.
According to the Central Weather Bureau, Taiwan's government agency tasked with seismic monitoring, the peak ground acceleration caused by the quake's seismic waves did not exceed more than 30 percent of a "g", the standard gravitational pull of the Earth. Seismic engineers call this amount of shaking "moderate". It will certainly be felt but should not lead to a catastrophic building failure, particular in a country like Taiwan, which has one of the most stringent earthquake resilient building codes in the world.
|Map: Complex plate tectonics under Taiwan. The red star depicts the epicenter of Saturday's quake. (Source: National Central University, Taiwan)|
Even though the blogger does not know the history of the Weiguan Jinlong residential building with its 96 apartments, something seems fishy: Damage in cities hit by moderate or strong earthquakes is never concentrated just in a single building. If only one building fails catastrophically and everything else is left standing with only cosmetic damage, one can only assume that the structure had a fundamental flaw in its design, or that its construction was very shoddy.
The reason that Taiwan has such stringent and mostly well enforced building codes is the island's location. The country sits on one of the tectonically most complex regions in the world, at the boundary between the Philippine Sea and Eurasia plates. There the two plates converge with a velocity of about 3 inches per year. However, the collision of the two plates is not straight forward subduction like under South America. North and east of the island, the Philippine Sea plate subducts beneath Eurasia along the Ryukyu Trench. South of the island, the South China Sea (on the the Eurasia plate) subducts beneath the Philippine Sea plate in the Manila Trench.
Besides the earthquakes associated with this complex subduction, Taiwan is often pummeled by temblors originating within the island's crust itself. Taiwan is dissected by a major north-south trending fault, which leads to devastating thrust earthquakes. The strongest of these occurred in April of 1935 and cost 3200 people their lives. The location of the so called Chi-Chi Earthquake on September 21, 1999 was also on this thrust fault, its epicenter a mere 60 miles from Saturday's quake. It had a magnitude of 7.6 and more than 2500 people were killed. The Taipei Times, an English language newspaper in Taiwan, reported on Sunday that the company which built the now-collapsed towers in 1994 was also involved in the construction of some of the structures which collapsed during the Chi-Chi earthquake. (hra115)
It does not happen very often, that scientists are invited to the White House. Of course, once you've received a Nobel Prize, every president is happy to pose with you for a photo opportunity. Or you may have achieved something special in your research, and be honored with the Medal of Science. Or perhaps you have even discovered something very special, for which you deserve the Presidential Medal of Freedom - but don't count on it. Since the inception of the Freedom Medal in 1960, only 19 scientists have been bestowed with this high honor. So when a whole group of West Coast seismologists, among them several from our Berkeley Seismological Laboratory (BSL), gather at 1600 Pennsylvania Avenue in Washington on Tuesday, something unusual must be going on.
John Holdren, President Obama's Science Adviser, has invited experts to the first ever "White House Earthquake Resilience Summit". Politically, this is an unusual move indeed. When we look at the history of earthquakes in this country, we find that politicians and administrations mostly act retroactively: Only after a big temblor has caused major damage, are funds made available to strengthen buildings and structures, educate the public about earthquake risks, improve seismic networks or upgrade earthquake research facilities. In contrast, Tuesday's gathering is a proactive step. The folks in the White House Office of Science and Technology Policy want to strengthen earthquake resilience now, before the next Big One happens.
Rumor is that this initiative was triggered by an article in the New Yorker in the summer about the long trong earthquake in the Pacific Northwest. But this great story alone wouldn't have done the trick. Seismologists also have something important to offer to the public, which may indeed save lives during the next big quake. Their efforts in developing an Earthquake Early Warning (EEW) system for the West Coast are slowly paying off. The demonstration system, which has been operational for several years is ready to be upgraded to a "Prototype Production System". Instead of having a couple of computers scanning the seismic records continuously for signs of an earthquake, the upgrade uses a robust network of linked computers with a lot of redundancy to automatically perform the scans and run the warning algorithms. This new system is a collaborative effort between the BSL, Caltech in Pasadena and the USGS offices in Menlo Park and Pasadena.
However, even though it has the word "Production" in its name, the new system is still not ready for a big time roll-out to the public. Currently only a few beta-testers like BART and emergency management agencies in the Bay Area and in LA receive the alerts. The reader may rightly ask, why this system is not available to everybody, like similar warning systems in Japan, Taiwan and Mexico. There are at least three important reasons, which are holding us back. To make the warnings faster and more reliable, many more additional seismic stations are needed, particularly in Northern California, Oregon and Washington. In addition, we need to develop multiple ways to deliver the warnings to the public within fractions of a second. There are many means of distributing such warnings, from cell phone apps, emails, and sirens, to automatic announcements on TV screens and through the radio. But each of them has to be fast, reliable and also robust. The last thing one wants is that a hacker gets into the system and spreads false messages about impending shaking. And thirdly, a huge educational effort is needed to teach members of the public what to do, when an EEW message is received.
While seismologists have laid the foundations for Earthquake Early Warning, it is now up to all levels of government and the private sector to finish the job and bring this system to life. Tuesday's meeting at the White House seems like a good start. (hra114)
The second significant seismic event of the still very young year 2016 was not an earthquake at all. The first event last Sunday (Pacific time), a tectonic earthquake with a magnitude of 6.7, caused major damage in the far northeastern corner of India near the border with Burma. Several hundred people were either killed or injured. The next event, on Wednesday, had a much lower magnitude and did not cause any direct harm, but it was politically far more significant: The Democratic Peoples Republic of Korea, commonly known as North Korea, detonated its fourth nuclear weapon since the beginning of its atomic weapons test program in 2006. Seismometers all over the globe registered the seismic waves from this underground explosion. Politicians of all major countries, even North Korea's allies in China, expressed outrage. In the meantime, the propaganda machine in North Korea's capital Pyongyang jubilated, that for this latest weapons test, the country successfully detonated its first hydrogen bomb.
North Korea is currently the only country in the world which conducts nuclear weapons tests. Its test site Punggye Ri in the province of North Hamgyong is located about 235 miles northeast of Pyongyang and about the same distance to the southwest from the Russian Pacific port city of Vladivostok. North Korea began testing atomic weapons there in 2006, with further detonations in 2009 and almost three years ago on February 12, 2013. These tests have gotten progressively bigger. This can be inferred from the equivalent earthquake magnitudes computed from the strength of the explosions' seismic waves. These values increased from 4.3 in 2006, to 4.7 in 2009 to 5.1 in 2013.
According the the calculations of the scientists at the USGS National Earthquake Information Center (NEIC) in Golden, Colo., Wednesday's event also had a magnitude of 5.1. Germany's Geoforschungszentrum in Potsdam estimated a slightly higher magnitude of 5.2. Based on more than 2100 nuclear weapons test conducted by the five official nuclear powers (US, USSR, Britain, France and China) during the Cold War, these magnitude values can be converted into the strength of the explosion, the so called "detonation yield". Usually, an underground nuclear explosion which generates seismic waves with a magnitude of 5.1 has roughly the same yield as the detonation of about 7000 tons of the conventional chemical explosive TNT. As a comparison: the atomic bomb which destroyed Hiroshima close to the end of World War was about twice as strong as this explosion.
While seismological research has made it possible to determine the yield of an underground weapons test with reasonable accuracy, we seismologists can't tell which type of weapon was detonated. Therefore it remains to be seen, if North Korea's claim of having successfully tested a hydrogen bomb is true. However, even if Wednesday's test was used to perfect a "regular" atomic bomb, it is scary enough. (hra113)
When two earthquakes with magnitudes of 7.6 struck the Latin American country of Peru on Tuesday evening (local time) within five minutes of each other, one had to fear for the worst. After all, in contrast to its southern neighbor Chile, Peru is not known for its earthquake resistant structures and strictly enforced building codes. But, although the shaking of both quakes was widely felt across western South America, it caused hardly any damage. Even in the epicentral region in the sparsely populated Peruvian jungle near the Brazilian border to the east of the Andes, no buildings collapsed. The head of Peru's emergency services, Alfredo Murgueytio, was quoted by Reuters as saying that "there are no damages reported." Several residents of the Brazilian city of Brasileia, 150 miles east of the epicenter, told the same news agency, that they felt the ground shake and that chairs and tables rattled during the quake, but that there was no visible damage.
At first glance, the absence of any significant damage was very surprising. After all, the single quake which occured earlier this year in Nepal wreaked havoc in Kathmandu and other areas of the Himalayas . It had a magnitude of 7.8 and hence was only slightly stronger than Tuesday's double temblor.
What is so different about these two earthquakes in Peru and the one in Nepal? The Nepal quake caused massive destruction with over 9000 casualties while the doublet on Tuesday hardly damaged anything at all. The main reason for the mild effects of the two Peruvian earthquakes was their focal depth. While the Nepal earthquake had its origin less than 10 miles below the surface, seismologists at several seismological centers around the world calculated the depth of the Peru double quakes to be between 375 and 400 miles below the surface. By the time seismic waves from such deep earthquakes reach the surface, they have lost a lot of their initial energy.
Think about what would happen when an earthquake with a magnitude of 7.6 were to occur in the Los Angeles area. While we are sure that it will cause quite a bit of damage in the epicentral region down south, we do not expect this earthquake to cause significant structural damage in the Bay Area. The seismic waves may be felt in our area around the San Francisco Bay, but they will have lost much of their punch on their almost 400 mile long journey way northward. It so happens that the distance between San Francisco and LA is similar to the depths of Tuesday's earthquakes in Peru.
While deep earthquakes like the two on Tuesday under Peru are usually rather gentle on buildings and structures on the Earth's surface right above their focus, they can be felt over a surprisingly large area. A magnitude 8.2 quake, which had its source almost 450 miles below Bolivia in 1994, made skycrapers in Toronto sway. Similarly, the deepest earthquake ever measured, the magnitude 7.8 quake in the Izu-Bonin-Trench in late May this year, caused a slight swinging movement of a 50 story building in Pasadena. The distances between Bolivia and Toronto and the Bonin Trench and Southern California are 4500 and 5500 miles respectively.
What is the reason for such ultra-long distance effects? In contrast to shallow focus quakes, the seismic waves of deep temblors do not have to travel through the Earth's crust on their way to distant locations. They start their journey in the Earth's mantle. Compared to the Earth's crust, this section of the Earth's interior is much more homogeneous, and therefore attenuates seismic waves much less strongly than the more heterogeneous rocks of the crust.
In summary: deep earthquakes usually cause less damage than shallower ones, but they can be felt over much, much longer distances. If you happen to be in a skyscraper which gently rocks from side to side, the motion is not necessarily due to the wind. The swaying of a tall structure can be caused by seismic waves from an earthquake continents away. (hra112)