How to protect yourself against earthquakes?

In our series of articles on natural catastrophes – how to protect yourself, we take a closer look at the topic of earthquakes in today’s article.

merkle-partner-security-against-earthquakes

In our series of articles on natural catastrophes – how to protect yourself, we take a closer look at earthquakes in today’s article.

Recent severe earthquake in Southern California

The 6. July 2019, 9:02 am California experienced one of the latest earthquakes in recent times. The quake reached a magnitude of 7.1 and was felt as far away as Las Vegas.
The epicenter was 17 kilometers northeast of the small town of Ridgecrest and about 200 kilometers northeast of Los Angeles. Days earlier, there had been an earthquake of magnitude 6.4 in the same region.
It was the strongest earthquake in the region in the past 20 years. Fortunately, there were no deaths or serious injuries, but there were strong fluctuations of the buildings and the outbreak of several fires.
If you compare reports on earthquakes of the same magnitude in developing countries, the damage and the number of victims are considerably higher.
This shows that one is not arbitrarily at the mercy of earthquakes, but can build more earthquake-resistant structures by taking appropriate measures.

But first things first.

How do earthquakes happen?

Earthquakes are caused by tensions in the earth’s crust that are suddenly released. These stresses occur especially in places where continental plates meet. This is also the case in California in the example above.
Accordingly, there are areas that are more earthquake-prone than others.

Figure 1 shows the earthquake frequency since 1973. The boundaries of the continental plates can be clearly seen here.

Earthquake frequency since 1973

Accordingly, the earth can be divided into earthquake hazard zones. The figure below shows the zones for Europe.

Earthquake Zones-Europe

The course of an earthquake resp. of earthquake shocks is similar. The closer you are to the epicenter (area of the earth’s surface above the earthquake focus), the higher the accelerations that occur.

The schematic course of the accelerations over the period duration is shown in Figure 3.

Time course of an earthquake

The ground conditions of a site also play a role. Rocky ground transmits accelerations harder and more directly than a clayey subsoil.

Calculation method

Originally, the calculation methods for analyzing the behavior of buildings and machines during earthquakes originated in the construction sector. Here, often simplified quasi-static accelerations are applied. Dynamic effects, such as z.B. the excitation of natural frequencies, however, cannot be taken into account in this process. Conservatively, these effects are represented by additional exaggeration factors, which leads to sometimes highly conservative results.

A transfer of these methods to complex machines and plants is not very accurate, because the vibration behavior cannot be represented exactly by a static analysis. But as so often, it is important that such calculations can be easily recalculated and checked, not so much how accurate the result is in reality.

Therefore, the most diverse standards allow these simplified calculations under certain conditions.

On the other hand, a dynamic calculation in the time domain, based on the excitation of the ground, is too complex. Especially since the exact function of the movement of the subsurface as a function of time is not precisely known.

A reasonable solution with justifiable effort is a so-called response spectrum analysis, in which the acceleration amplitude is superimposed on the frequency or. period is applied and the response of the structure consists of conservative superpositions of the individual vibration modes.

In the assessment of components in airplanes, ships, trucks or military vehicles under vibration, we proceed in a computationally similar way, as an aside.

How can you protect yourself against earthquakes?

Merkle und Partner uses all common methods for the protection against earthquakes, depending on the requirements of our customers. The verifications can be performed according to all common earthquake codes (Eurocode, IBC, ASCE, SIA, GOST, NSCP, ASME, RCC-M, KTA u.a.) will be performed by us.
A distinction is made between whether a plant should only remain standing or whether its function must also be guaranteed after or even during the earthquake.
For primary pumps ASME Section III Class 1 of nuclear reactors, z.B. make sure that the pumps are working during an earthquake, otherwise there is a risk of a meltdown.

One of the most exciting projects was the design and verification of a HV-deck and a HV-bushing for the fusion reactor ITER in Italy, which is supposed to produce clean energy in a few decades without producing radiating waste.

As you can see, we have extensive experience in providing specially tailored proofs together with our customers.

No, of course not. It is only a question of the strength of the earthquake when a plant, no matter how well designed, will collapse. But just as the probability of a century earthquake decreases, the risk that buildings or facilities will collapse from even smaller earthquakes, which are comparatively more likely, becomes smaller.

We help you to identify and optimize earthquake-critical areas of your buildings, facilities and components.
Do your customers also require appropriate proofs for their investments or. Safeguards in the event of an earthquake?
Talk to us. We show you how we can support you competently and efficiently.

The contact person for these topics is Dr. Maik Brehm, Tel. +49-(0)7321-9343-137. He is looking forward to your call.

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