How is earthquake hazard composed?

Earthquake hazard, also referred to as seismic hazard, is composed of different input data, representing the main components of the updated earthquake hazard model of Europe.

Namely, the assessment is based on knowledge about past earthquakes, geology, tectonics, and local site conditions at any given location across Europe. The underlying datasets of these factors are combined into an earthquake hazard model that can be used to estimate where earthquakes of different sizes may occur, how frequently they are expected to happen, and how probable certain levels of ground shaking due to earthquakes are. Recent scientific knowledge and research results are also required in order to reliably assess and estimate the different ground shaking levels across Europe.

Earthquake catalogues

Earthquake catalogues

Past seismicity and historical earthquake recordings (e.g. location, magnitude and intensity) are key to understand and estimate future seismicity and ground shaking. In order to calculate the 2020 European Seismic Hazard Model, information about earthquakes from the year 1000 AD up to 2014 has been collected and compiled in so-called “earthquake catalogues”. 

Observed effects of past tremors are used to estimate the probable intensity, magnitude and location of these historical (“pre-instrumental”) earthquakes. Since around 1900, the recorded seismic waves from earthquakes have instead been used to estimate the magnitude, location and depth of these more recent “instrumental” events

All this information enables an estimate of the intensity of future earthquakes in a given area. Since the input to these earthquake catalogues is provided from many local or national seismic networks, the final catalogue needed to be harmonised to account for variations in the compilation of the different input catalogues.

Compared to the previous version of the European earthquake model released in 2013, the updated earthquake hazard model for Europe covers a wider range of magnitudes and includes an additional 1,000 historical events. This additional information on past earthquakes enriches the model with an extended dataset, leading to a more comprehensive seismic hazard analysis.

Geology & tectonics

Geology & Tectonics

Earthquakes occur due to the rupture of geological faults, triggered by the motion of tectonic plates in the earth’s crust. The joint interpretation of many earthquakes allows conclusions on the tectonic stress regime, which is fundamental for providing estimates on the earthquake hazard in combination with information on fault orientations. Identified rupture planes in combination with the associated sense of motion allow conclusions on the tectonic regime of a region.

It is important to collect information on the active faults that are present within a given region, including their location, geometry, and the relative slip between different sides of the fault. This data can help to understand the location and magnitude of future earthquakes, especially in regions where the earthquake catalogues are incomplete.

Researchers improved the active fault database for the updated European seismic hazard model by adding about 1,200 active faults, spanning over 90,000 km of mapped faults. 

How seismic waves propagate also depends strongly on the local geology. Therefore, extensive geophysical measurements are required to determine the influence of local geology on the recorded ground motions. 

The information on the stress regime in combination with identified faults and fault orientations is fundamental for estimating seismic hazard. State-of-the-art seismogenic source models have been developed for the updated version of the European earthquake hazard model to capture the spatial and temporal pattern of earthquakes across the Euro-Mediterranean region.

Ground shaking models

Ground shaking models

The physics related to the radial propagation of seismic waves from the hypocenter (where the fault ruptures) through the earth's crust, together with data from past earthquakes, allow us to estimate the ground shaking level at specific location due an earthquake with a certain size.

New ground motion models have been developed for Europe’s updated earthquake hazard model through the newly compiled recordings of strong ground shaking and enhanced metadata of 25,000 waveforms.

Where to access earthquake hazard data?

The hazard.efehr platform operated by the Swiss Seismological Service (SED) at ETH Zurich provides interactive access to the input data of the models’ components. In addition, the scientific data is accessible on the publicly available EFEHR GitLab repository for free download. Please observe the license and copyright information.

How to cite:

Whenever making use of scientific products such as input filesor when distributing visualizations of the 2020 European Seismic Hazard Model (ESHM20), please refer to:

Danciu L., Nandan S., Reyes C., Basili R., Weatherill G., Beauval C., Rovida A., Vilanova S., Sesetyan K., Bard P-Y., Cotton F., Wiemer S., Giardini D. (2021) - The 2020 update of the European Seismic Hazard Model: Model Overview. EFEHR Technical Report 001, v1.0.0, https://doi.org/10.12686/a15