Macroseismic

Macroseismic refers to the observation, description, and analysis of the effects of earthquakes on the surface, on structures, and on people. It focuses on macro-scale manifestations of shaking rather than the physical processes at the source or within rocks. The discipline, often called macroseismology, relies on reports of perceived shaking, damage patterns, ground cracks, landslides, and other surface phenomena to characterize an earthquake’s impact at different locations.

A central concept in macroseismology is the intensity of shaking, typically expressed on empirical scales. Historical scales include the Rossi-Forel scale, the Medvedev–Sponheuer–Kárník (MSK) scale, and the Modified Mercalli Intensity (MMI) scale. In Europe, EMS-98 (European Macroseismic Scale 1998) is widely used. These scales translate qualitative observations into numerical values, enabling the construction of isoseismal maps that depict regions of equal shaking intensity around an epicenter.

Data collection methods involve field surveys and structured questionnaires to gather eyewitness reports, as well as analysis of visible damage to buildings and infrastructure. Today, macroseismic data also come from online reports and social media, which supplement traditional surveys. Applications include hazard assessment, calibration of ground-motion prediction models, and historical earthquake analysis, especially where instrumental records are sparse or absent.

Limitations arise from subjectivity in perception, differences in construction and maintenance, and local site effects that can amplify or dampen shaking. Macroseismic data are most effective when integrated with instrumental seismology to provide a fuller picture of an earthquake’s effects and to improve understanding of ground shaking in a region.