"If we do nothing, a national disaster will occur"

This is the opinion expressed by Prof. Avi Shapira - Chairman of the Steering Committee for Earthquake Preparedness, Prof. Shmuel Marko from Tel Aviv University and Prof. David Yankalvski from the Construction Research Center at the Technion

The earthquake that happened on Friday at noon surprised the experts in Israel, not so much in its strength - it is considered a relatively weak earthquake, only 5.3 on the Richter scale. The surprise was in two other components of it - its location in an area that was not known as an active geological fault, around the city of Tire in Lebanon, and the fact that, despite its low intensity, it was well felt at a great distance from the epicenter. Even on relatively low floors in Tel Aviv, which is about 250 km from the center of the noise, it was felt in the shaking of the buildings.

However, an earthquake of this magnitude should not worry the experts, but all the experts we spoke with believe that since Israel is near active faults, and given the long history of strong earthquakes, we must prepare. Prof. Avi Shapira, chairman of the Steering Committee for Earthquake Preparedness, says in a conversation with the Hedaan website: "This earthquake is a good reminder to all of us that we need to take preparatory actions. The field where more needs to be done than in any other field is in the field of buildings. There is no other solution but to build correctly so that the building does not collapse on us. There are quality standards regarding the construction that is carried out today, but there are many buildings that we know do not meet any standards and they must be strengthened. We implore the government to accept the proposal of Infrastructure Minister Binyamin Ben Eliezer to immediately strengthen public buildings, especially schools and hospitals. These preparations will allow us to minimize the disaster, and prevent a situation where a strong earthquake will turn into a national disaster. If we don't do anything, this is what will happen." Prof. Shapira adds that according to the law, it is allowed to build anywhere, except for active geological fractures, provided that the building meets the standards.

What is the role of the committee?

Prof. Shapira: "The committee is trying to coordinate all the factors in the State of Israel to address the whole range of issues related to Israel's preparation for earthquakes. Apart from the prevention, which I mentioned, it is also necessary to take care of the response area. We must determine in advance who is responsible for what, and what falls under the responsibility of each government ministry; Which entities in the State of Israel are involved; to identify in advance where there are gaps in the preparation, and how they can be covered; And of course the long-term rehabilitation needs to be taken care of afterwards. Right now, the committee is dealing with two of the three phases - the preparation and the immediate response."

To assess what the construction industry is doing to prepare for earthquakes, we turned to Prof. David Yankalevsky, head of the National Institute for Construction Research at the Technion: "Buildings plan for some reference earthquake, not knowing necessarily, but choosing a reference earthquake that is strong enough, but certainly knowing that with some probability we may be hit Strong vibrations from her. However, the concept of planning does not hold that until an earthquake with the intensity of the reference earthquake everything should be fine and with a slightly stronger earthquake it is allowed to cause complete destruction. The concept is of gradualness in the building's ability to deal with the strength of the earthquake, so we want even if we are affected by a stronger earthquake than the reference earthquake, we are ready to absorb greater damage to the building, but on the condition that it preserves its integrity."

And what is that reference tremor?

Prof. Jankalevsky: It is impossible to quantify the answer with a number - because the intensity of the earthquake is only one of the factors affecting the rate of damage. There are other factors - for example, the location of the noise center. In every region of the country you have to prepare for all possible combinations. The Geophysical Institute constantly updates its maps according to the accumulated knowledge. It is certainly possible to prepare the structures for ground accelerations with a higher intensity than the reference intensity, but then this makes the structure very expensive. An optimum point needs to be found because of the relatively low probability of large earthquakes occurring. New buildings are already supposed to be built according to the standard that refers to the most updated map. Regarding existing buildings there is a problem, the buildings were almost certainly not designed according to some earthquake standard, and even if they were designed to a standard that was accepted 30 years ago, a period when there was already an Israeli standard for designing buildings for earthquakes, even then it will be at a disadvantage compared to a new building that will be built near it according to the latest standards.

What do we do with the existing construction?

"In principle, there are options to upgrade the resistance of buildings to earthquakes, this can be done by strengthening them, i.e. increasing their resistance, or by upgrading them, i.e. giving them a greater ability to absorb energy without the need to strengthen them to the same extent. One of the options that is on the table is to add a tower of dimensions to the apartments, thus allowing them to withstand not only the enemy's artillery but also earthquakes. Another option is to strengthen walls by adding steel beams in the appropriate places, then increasing the ability of the structure to absorb energy. This reinforcement can make the difference between a brittle structure that was about to fail in a small shake, and a structure that will maintain its integrity even after a strong earthquake. This is the small difference between burying people while alive in the ruins of a dilapidated building or a building that, even if damaged, still maintains its integrity more or less and people can be rescued from it unharmed."

Prof. Jankalevsky criticized a published study October 2007 Jointly led by Dr. Oded Katz from the Geological Institute and Dr. Shmuel Marko from Tel Aviv University, where the researchers determined that a very strong earthquake is expected along the Dead Sea rift. This is in light of the relative peace in the last thousand years.

In a conversation with the Ydan website today (Sunday), Marko comments on this: "Although it is impossible to accurately predict when an earthquake will occur, we can predict most of its other characteristics. We can talk about location, power, possible damage. We can predict the time but not at the operative level. It's like predicting roughly when the first rain will fall next year. We can estimate it in the range of October plus or minus a month but not exactly a day. Or if we take another example - car accidents. The fact that we cannot predict which road and which car will be involved in tomorrow's accident does not mean that we do not know that there will be an accident tomorrow. It is clear to us that tomorrow there will be a road accident in Israel and it is clear that we need to prepare for it both by improving the infrastructure of the roads and vehicles and by evaluating the emergency services."

Prof. Marko explains that historical sources and observations at archaeological sites show that for a very long time there has not been a strong earthquake in the Dead Sea rift in the section between the Dead Sea itself and the Sea of ​​Galilee. After a series of roughly 7 degree earthquakes that began in 31 BC (an earthquake that Josephus Flavius ​​described in detail in his book Wars of the Jews) and continued with earthquakes in 363, 749, and 1033. Since then there has been "quiet" and except for relatively small earthquakes of approximately level 6 such as the one in the north of the Dead Sea on 11/7/1927 and which hit Jerusalem and its surroundings (and which also caused about 250 deaths) no strong earthquakes occurred. "The fact that for a thousand years there were earthquakes at intervals of 400 years and then a thousand years pass without any significant earthquake tells us that the tension in the area is double what it was in the periods preceding the earthquakes before. The calculation is indeed complicated, not linear, but the models show that such an earthquake could be stronger."

It should be noted that the study only referred to earthquakes originating in the Dead Sea rift, and not, for example, the great earthquake that destroyed Safed on January 1, 1837. At that time, the epicenter was in the region known as Rum, which stretches from Metula towards the Mediterranean Sea south of the capital. The earthquake that occurred on Friday in Tire did not occur on a familiar replica.

What is the practical significance of this prediction?

Prof. Marko: "From a practical point of view, this means that we need to be prepared, like for traffic accidents, we need to be prepared on a general level, starting with the enforcement of building codes, through the organization of the state in preparation for a disaster, since we are not that organized by our nature. In this case, it is of critical importance to decide in advance what each authority does, through education of the residents. I lived for a while in California, where every child from kindergarten age goes through practice. He knows where there are iron boxes with flashlights, bandages and first aid equipment, and at the university you are not allowed to enter the first class without going through an orientation that shows you where to run in case you start to feel an earthquake, and of course everyone is taught how to behave at home, such as anchoring libraries or stretching straps to prevent bottles containing substances Dangerous to fall (especially in chemical warehouses) in case of earthquakes. Through these simple actions, a lot of damage can be prevented. In California, in every supermarket, and in every public place there are instruction booklets. These are things that don't cost much and that could be done here as well."

More information

An article by Prof. Jankalevsky about the need to prepare buildings for earthquakes

Articles on the science website

A strong earthquake must occur soon (see the body of the article)

When will the next earthquake occur?

Damage is expected in a major earthquake soon

How do you protect houses from a strong earthquake?