The next quake is definitely coming. And maybe it will be the catastrophe that geologists have long been warning about. San Francisco, Istanbul, Tokyo - all of these cities must worry about serious earthquakes. And many other cities in different parts of the world as well.
They are located in geologically highly sensitive areas where the continental plates of the earth's crust meet. There is growing tension in the underground, gradually. And one day, this tension will be discharged suddenly - with probably catastrophic consequences.
But what about Bottrop-Kirchhellen, Plauen or Müllheim? Germany is located in the middle of the Eurasian plate, plate borders are far away here - and yet in this country again and again the ground shakes. Reason are breaks and weaknesses in the underground, which can cause problems.
If, for example, in the south of Europe, the African meets the Eurasian plate and piled up the Alps, not all the pressure will be absorbed. The rest of the gigantic forces let the Upper Rhine Graben torn apart bit by bit, the earth in the area keeps shaking.
The conclusion of geo-researchers is therefore that the risks of earthquakes in Germany are low - but they are not negligible. Now experts have presented new maps on earthquake hazard in the country. It replaces the currently valid earthquake zones, which were last revised about 20 years ago, in the building standards. There are no fundamentally new findings, but compared to earlier maps, the participating researchers see their results as "significantly better hedged".
G. Grünthal et a
Earthquake risk in Germany, registered quakes since the year 1000
Responsible for the work is the German Geo Research Center in Potsdam, whose experts also report on their work in the journal "Bulletin of Earthquake Engineering". You have worked on behalf of the German Institute for Construction Technology and in coordination with the relevant DIN standards committees - and say: "The reassessment will have far-reaching economic consequences." At least that's the view of GFZ expert Fabrice Cotton. The maps would be part of the "National Annex" of the new DIN standard DIN EN 1998-1 / NA, so Cotton. This means that builders in endangered areas will in future have to be careful to design their buildings earthquake-proof according to the new regulations.
For the new maps of the earthquake zones, the GFZ researchers had statistically evaluated a list of the earthquakes known in the past on the territory of today's Federal Republic and the neighboring regions - in the years 1000 to 2014. They also identified numerous events that were included in past hazard calculations had flowed, even though it was not quakes to today's findings.
In some cases, storms, sudden subsidence or reports of distant earthquakes have been recorded as local events. "More than 60 percent of the damage quakes listed in the previous German earthquake catalog have never taken place in some areas," says study author Gottfried Grünthal of the GFZ. "Later chroniclers or authors of seismic catalogs simply took over the mistakes."
As an example of such a "fake quake", an earthquake that never took place, Grünthal calls the earthquakes that shook the city of Neuburg on the Danube in 1591. They found themselves in many earthquake lists - and go back to a contemporary report that there was damage to a rectory in the region. This, according to the researchers after reviewing other documents, however, is likely to go back to a well-documented earthquake, which took place a year earlier in neighboring Lower Austria. For its own quake in 1591 there is no evidence.
earthquake intensities
The Richter scale
The magnitude of an earthquake is described using the Richter scale and other scales. The specified value, the magnitude , indicates the released energy.
Seismographs are used to determine the maximum amplitudes (that is, the deflections of the needle) that would have been converted by earthquakes 100 km away. The decadic logarithm of the measured maximum amplitudes gives the magnitude. The increase of the magnitude by 1 means a 33 times higher energy release - an earthquake with a magnitude of 5.0 is thus 33 times as strong as one with a magnitude of 4.0. The scale was developed in 1935 by Charles Francis Richter and Beno Gutenberg at the California Institute of Technology.
Strictly speaking, however, earthquake strengths are given today in the moment magnitude scale . In addition to the energy, it also takes into account the size of the broken rock. The fracture surface can be calculated from the seismic measurement of many seismographs.
The effects
Roughly, the typical effects of the earthquakes near the epicenter can be described as follows:
- - Strength 1-2: only detectable by instruments
- - Strength 3: rarely felt near the epicenter
- - Strength 4-5: 30 kilometers around the center noticeable, slight damage
- - Strength 6: moderate quake, death and serious damage in densely populated areas
- - Strength 7: strong earthquake that can lead to catastrophes
- - Strength 8: Great Quake
Not included in the analysis were such seismic events related to human activity, such as coal and salt mining, oil and gas exploration or geothermal energy. Because they would have little meaning in the long term.
Roughly speaking, Germany's earthquake areas lie to the west, south and southeast: the Lower Rhine Bay, the Rhine ditch and the Lake Constance region, the Black Forest and the Swabian Alb, the Vogtland.
Damage in the hundreds of millions
In the border region between Germany and the Czech Republic, for example, there have been more than 100 minor earthquakes since Ascension Day. These so-called swarm quakes did not cause any damage. Even in Baden-Württemberg and the North Rhine-Westphalian border region with the Netherlands, the earth shook last, even without dramatic consequences.
For example, the tremors that were registered in April 1992 in the border area between Germany and the Netherlands have shown that major damage can also occur in quakes in Germany. The so-called earthquake of Roermond at that time had a strength of 5.3 and caused damage in the hundreds of millions. It was the strongest earthquake in Germany for almost 250 years.
And so far as hitherto regarded as safe areas have to deal with the issue: Geoforscher had warned in mid-May that in the region of Halle-Leipzig might also threaten similar violent shocks such as in Roermond. The scientists analyzed smaller earthquakes in 2015 and 2017 - and found evidence that previously accepted as calm geological fault zones could be reactivated in the underground.
The General Association of the German Insurance Industry had then pointed to the - in his view - poor insurance coverage of many households. In the federal section, 41 percent of all households are insured against natural hazards such as earthquakes - so-called elemental damage. This requires an "extended natural hazards insurance", which also covers landslides and subsidence as well as floods, heavy rainfall, snow pressure and avalanches.
However, the number of insured persons differs greatly from one federal state to another. While 94 percent of households in Baden-Württemberg are protected by appropriate policies, their share in neighboring Bavaria is just 32 percent. (A complete list can be found here.)
The total damage caused by earthquakes in Germany is not that easy to determine. The insurers only show the damage costs for "Erdgefahren", but besides earthquakes also earth and mud slides as well as earth subsidence are recorded. The latest information comes from the year 2015. At that time the sum was 4.3 million euros.