28. Magnitude and Intensity of Earthquakes
Understanding the magnitude and intensity of earthquakes is vital for engineering seismic-resistant structures. Magnitude indicates the energy released at the earthquake's source, while intensity measures the shaking effects experienced at specific locations. The chapter explores various scales used to quantify these parameters, their relevance in structural engineering, and how they influence seismic design.
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What we have learnt
- Magnitude measures the energy released by an earthquake, while intensity assesses the shaking experienced at specific locations.
- Different scales like Richter, Moment Magnitude, and Modified Mercalli are used to quantify magnitude and intensity.
- Local geology, building construction, and distance from the epicenter influence the intensity of shaking experienced during an earthquake.
Key Concepts
- -- Magnitude
- The amount of energy released at the source of an earthquake, typically measured on scales such as the Richter or Moment Magnitude Scale.
- -- Intensity
- A measure of the shaking effects of an earthquake experienced at specific locations, often reflected in scales like Modified Mercalli Intensity.
- -- Seismic Hazard Zone
- Areas classified based on the likelihood of experiencing earthquake effects, which guide earthquake-resistant design criteria.
- -- Attenuation
- The decrease in earthquake ground motion amplitude and energy as distance from the source increases.
- -- Isoseismal Maps
- Maps that depict the distribution of seismic intensity across a region following an earthquake, using contour lines to connect areas of equal intensity.
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