Earthquake Ground Shaking Scenarios
At Quantectum, we generate maps illustrating global earthquake ground motion and shaking intensity of earthquakes with a magnitude of 5.5 and above. These maps play a crucial role in evaluating seismic hazards and risk by transforming earthquake data into actionable insights, such as creating exposure maps for urban areas and populations.
This process is essential because a fundamental aspect of seismic hazard and risk assessment revolves around estimating the anticipated earthquake ground motion and level of shaking intensity associated with significant earthquakes.
In practice, when we know details about an earthquake, like where it occurred, how big it was, and how it moved, we use special equations called "Empirical Ground Motion Prediction Equations" (GMPEs) to figure out values of earthquake ground motion parameters of engineering interest, i. e., how fast the ground shook. These are Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), and Elastic Response Spectra in Acceleration. These GMPE equations are based on past earthquake data.
Macroseismic intensity is a way to describe how strong an earthquake feels in a more human-friendly way. It's like a scale that tells us how people perceive the shaking, what happens to objects, and how buildings might get damaged.
Producing Earthquake Ground Motion Maps
In Quantectum, maps of Peak Ground Motions and intensities are automatically generated a few minutes after the occurrence of earthquakes worldwide having a moment magnitude of 5.5 (Figure 2). In the process, we consider different approaches for shallow crustal earthquakes and subduction earthquakes. Derived products are also proposed, such as cities and population exposure maps (Figures 3 and 4).
Based on the concept of “ShakeMap,” originally developed by the US Geological Survey (USGS), these maps are useful tools to assess the extent and the severity of felt shaking by population and the distribution of damage produced by moderate to large seismic events.
Earthquake ground motion scenarios computed from Quantectum earthquake forecasts and prognosis are also provided to anticipate better and mitigate potential future earthquakes. They facilitate notification of shaking alerts at user-selected critical facilities and can be used by public and private institutions to plan emergency response and to produce loss models.
Figure 1: From basic seismological information (1), flowchart of the generation of earthquake ground shaking maps in terms of (2) ground motions parameters and (3) macroseismic intensities. The image on the left (Basic Seismological Information) serves as the starting point for creating earthquake ground-shaking maps. It includes fundamental seismological data about the earthquake, such as its location, magnitude, and details about the fault mechanism. These essential pieces of information are crucial for understanding the earthquake's characteristics. The image in the middle (Ground Motion Parameters) represents the next step. In this part of the process, seismic experts use the data from the left picture to calculate various ground motion parameters. These parameters include Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), and elastic response spectra in acceleration. These measurements help quantify how much the ground shakes during the earthquake and provide valuable data for assessing potential effects on structures and people. The image on the right (Macroseismic Intensities) shows the final step in generating earthquake ground shaking maps and involves converting the ground motion parameters from the middle image into macroseismic intensity values. Macroseismic intensity is a qualitative and discrete scale that reflects the human perception of shaking, its impact on objects, and the potential damage to buildings and infrastructure. This information is presented visually to help people understand the potential impact of the earthquake in their area.
Figure 2: Example of estimated macroseismic intensities from the April 14th, 2016, Mw6.2 earthquake that occurred in Japan. Macroseismic intensity is used to classify the severity of earthquake ground shaking on the basis of observed effects in a limited area and estimate the potential damage to the environment.
Figure 3. Macroseismic intensity can be estimated for individual cities potentially exposed to earthquake shaking.
Figure 4. Similarly, Quantectum can estimate how much of the population was exposed to different levels of macroseismic intensity.