字幕表 動画を再生する 英語字幕をプリント Istanbul straddles a strait between Europe and Asia. Time and time again, it's shaken by unpredictable, strong earthquakes. Istanbul is extremely at-risk. Over the past fifty years, this megacity has grown from a population of about one Million residents to fifteen Million. It's a race against the clock, posing a challenge to disaster management teams, and local residents. The city lacks buildings that can withstand quakes. 95 percent of all houses would have to be demolished. We face a terrible situation. It's not just the quake itself, it's the aftermath too. Is it possible to predict the next big earthquake? Seismologists are developing a new method. The best-case scenario would be to put out a sort of “fever curve,” where every day we could estimate if there's a higher or lower risk of an earthquake. But forecasting too far in advance has risks of its own. People would storm the banks. They would storm the stores. They would turn on each other. Are there security forces or a plan in place for this type of scenario? No! The countdown for seismologists and emergency responders is on. More than 15 Million people live in this coastal city. And it is becoming increasingly crowded. The Bosporus Strait divides Istanbul into a European and an Asian side. The region is particularly prone to earthquakes. In 1999, less than one hundred kilometers from the city center, an earthquake strikes. It's one of the worst in Turkey's history. At least 18,000 people die. Hundreds of thousands are left homeless. Emergency responders are often too late. There is no working emergency plan or early warning system in place. Thousands of buildings collapse like houses of cards. Sandy subsoil and shoddy construction are to blame. Seismologists expect a similarly powerful earthquake in the coming years, this time right off the coast of Istanbul. A good 1700 kilometers away: At the German Research Centre for Geosciences in Potsdam, scientists monitor earthquakes all over the world. Seismologist Marco Bohnhoff and his team are studying the city on the Bosporus. The earth's crust is especially unstable in the region. Istanbul is extremely at-risk. Over the past fifty years, this megacity has grown from a population of about one Million residents to more than fifteen Million. And unfortunately, just off the coast of Istanbul, there's an active plate boundary and from what we can tell, it's under enormous stress. A tremendous amount of energy is currently building up underground. Like all continents, Europe sits atop tectonic plates. Directly in front of Istanbul in the Sea of Marmara, the Eurasian plate meets the Anatolian plate, forming a so-called fault zone. Typically, these plates push past each other bit by bit. And gas bubbles rise from the ocean floor. We can see this from footage taken by a French-German-Turkish research team. But right off the coast of Istanbul, the plates are stuck. We don't see the usual gas bubbles. At spots where the earth's plates cannot move alongside each other, the pressure builds. Energy accumulates. If it discharges, the plates could move forward by up to 5 meters at once... ...triggering a violent earthquake... ...right in front of the coastal city. The government forecasts 30,000 to 80,000 deaths could result. Experts even say a tsunami is likely, with waves as high as four meters. Seismologists predict the earthquake will have a magnitude of at least 7. Earthquakes are measured on a scale of 1 to 9.5. Quakes with a magnitude of 4 are felt by most people in the area. A magnitude 7 quake is considered particularly strong. Bohnhoff's team wants to use a new method to predict powerful earthquakes like these in the future. There is a series of indicators we can observe before an earthquake strikes. And if we can systematically record and evaluate them automatically in real time, it would be essentially be possible to look at the fever curve of a fault zone 24 hours a day. And then issue warnings when necessary. That would be revolutionary. So far, early warning systems around the world react - at most — a few seconds beforehand. So-called “seismographs” register the less powerful primary waves of an earthquake, sending a signal just seconds before the destructive secondary waves start. Mexico City uses such a system. In 2017, there were two particularly strong quakes here. About 20 seconds beforehand, residents were warned via public loudspeakers, saving thousands of lives. This was possible because the epicenter of the quake was far outside the city. In 2011, Tokyo experienced one of the most severe earthquakes ever seen worldwide. The city's residents were warned via television, radio and the Internet nearly 80 seconds beforehand. In those precious seconds, the city can shut off gas lines, switch traffic lights to red and bring trains to a halt. Istanbul also has an early warning system. But it's only for the disaster management team. And the warning period is limited to just 5 seconds. At the Disaster Coordination Center, that is not enough time to warn residents. Because that time span is so short, people would not be able to escape in the event of a quake. That's why our system is limited to preventing accidents or fires, for example by automatically turning off the gas. Employees of local transportation and gas utility as well as firefighters are often on standby in case of an earthquake. They also get some help from the computer software, ELER. Depending on the magnitude and location of the quake, the program immediately calculates the number of potential deaths or collapsed buildings. Then we have to compare the computer's estimation with what's actually going on. To do this, we use information from the team that's onsite, for example, the fire department. Then we can be confident we're sending the right team to the right place. Residents must also be prepared. At the Disaster Training Center in Kozyatağı, an eighth-grade class is running through drills today. So how close is the danger? This is the North Anatolian Fault Zone... We are only 12 kilometers away from it here in this district. That means a quake would be felt especially strongly here. A simulator generates a quake with a magnitude of 6.7. The children only have a few seconds to duck under the table. It's important they remember to protect their heads. When the quake is over, the students can run outside — but not before turning off gas and electrical appliances to prevent fires. I only knew a little about earthquakes before this. But now I've experienced it and understand what to do. The instructor, Cenk Tankal, recommends always having an emergency backpack ready to go: Equipped with water, a flashlight and a first aid kit. Professional aid won't come for the first 72 hours of a disaster. Therefore, we must be prepared for survival until help arrives. But these tips are only useful if buildings and infrastructure can withstand the earthquakes. On the European side of the city, a subway line is being extended. Civil engineer Mustafa Murteza is supervising the project on behalf of the municipality. In the district of Kağıthane, the tracks emerge above ground and cross a bridge. It is supposed to be safe for an earthquake up to a magnitude of 7.5. But the soil poses a risk. We have to cover a long distance here, but the ground is very muddy and unstable. This is dangerous during quakes. That's why we dug very deep into the earth to connect the bridge's pillars with stable ground. A 70-meter-long steel structure will anchor the bridge to firmer ground. The subway control center: This is where emergency plans should take effect in the event of a quake: stop elevators, switch escalators to move up only, slow down and evacuate trains. And then, while we're filming, this happens A moderate earthquake with a magnitude of 5.8 hits the city. It is the second earthquake within a matter of days. There hasn't been a situation like this for many years. I was at work. At first, I thought something struck my chair, then it started shaking. We were evacuated immediately. Now I'm here to pick up my child. Good luck! Cell phone service is disrupted. Those who can, try to reach their friends and family. The houses here are all old, so we are very afraid. I can't reach my family, the lines are down. I am also afraid to go home. I am nervous, very nervous. I can't even picture what the big quake would be like. Fortunately, there are no deaths or injuries. But many buildings, including this minaret, are damaged. One day later. Tayfun Kahraman is the head of earthquake risk management for the city. He's faced with a big challenge. The city's warning system did not activate during the quake. You can't say the system worked as it should have. We have 10 stations at the moment but we aren't receiving a signal from any of them, not even yesterday. Our task now is to build more stations and repair the 10 we already have. Turkey's conservative party ruled Istanbul for 25 years until the summer of 2019. Kahraman says the party did not do enough to prepare the city for earthquakes. Unfortunately, we cannot say that Istanbul is prepared for an earthquake today. There are still buildings here that are in danger of collapsing. After all, even the 5.8 magnitude quake caused major damage. The new city government wants to set new priorities. Today, Kahraman hosts representatives from the MAG-DER foundation at City Hall. For about two decades, this group of scientists, merchants and craftsmen have been trying to prepare Istanbul residents for the next big earthquake. Traumatized by the 1999 quake, they do not want to leave their fate in the hands of the state alone. Our mission is that within the first 72 hours after a quake, everyone is active in their own neighborhood. We want to train 4 to 5 volunteers in each district to form a civilian disaster rescue team. The new city administration wants to work together with the foundation. For disaster management expert Özden Işık, this is a ray of hope. We have come to the right place. He will support our projects, develop them further and he also has plans of his own. The earthquake was a wakeup call for the whole city. At a panel discussion, the foundation MAG-DER informs residents about the dangers of earthquakes. There's quite a bit of interest. Özden Işık tells them what they must avoid at all costs, is panic. When combating a disaster, the most important asset we have is people. But only if those people are prepared and can act reflexively. If they are not prepared, then they become a liability because they panic. Back in Potsdam, Germany. During laboratory tests, seismologist Marco Bohnhoff has a breakthrough. He uses various types of stone to simulate earthquakes. In the real world, there might be 100 or 200 years between two strong quakes. We do not have that time. So instead, we simulate these processes at an accelerated rate. We increase the pressure relatively quickly and then retrieve the measured values so we can do our calculations. Ultimately, we can recreate a complete cycle from one quake to the next within a few minutes. Bohnhoff tests it out with a sandstone sample. A press applies an enormous amount of pressure to the stone. The machine simultaneously registers acoustic signals that reveal what is happening to the stone internally. Slowly, the machine increases the pressure on the stone. It's as if 30 trucks were stacked up on one finger. On the surface, it appears the stone hasn't changed. But the acoustic signals on the monitor show another story: It's beginning to fracture. More and more cracks become visible - like small, miniature quakes. Fifteen minutes later, the stone breaks. Marco Bohnhoff says the same logic can be applied to large-scale earthquakes. We're seeing all of this foreshock activity before the point of fracture. And since that's similar for all rock samples, we are hopeful we can apply this method. Many mini-quakes to signal a larger earthquake is coming?