I feel the earth move under my feet: the history of earthquake intensity and magnitude

Near dawn on 6 February 2023, at 4:17 a.m. local time, residents of Pazarcık City in southern Turkey experienced powerful shaking. Witnesses described their experiences of being shaken from their sleep, some running to their cars for safety from the damaged buildings. “I have never felt anything like it in the 40 years I’ve lived,” said Erdem, a witness living in Gaziantep. “We were shaken at least three times very strongly, like a baby in a crib (Brewer & Kerley, 2023).” The degree of utter devastation by the earthquake and its aftershocks were displayed on social media via videos posted by people in Turkey and Syria. The world watched helplessly as horrifying images of collapsing buildings and shattered lives in Turkey and Syria were beamed on screens and printed in newspapers. The death toll from this disaster reached 45,000 in Turkey and about 5,000 in neighbouring Syria. According to news reports, this phenomenon hurled more than 160,000 buildings, containing 520,000 apartments, off their foundations and damaged other infrastructure as well. It was the worst disaster in Turkey’s modern history (Reuters, 2023). The extent of surface ruptures associated with the shaking has been mapped using satellite imagery and ground observations. Images captured before and after the earthquakes show sharp discontinuities in displacement, revealing two separate zones of surface rupture (Sommerville & Evans, 2023). From the reports given, it is obvious that different people use different ways to describe the size or power of such an event. The first witness above described the phenomenon based on a feeling of being shaken very strongly, “like a baby in a crib.” For many watching the videos, the size of this phenomenon was based on the reported death toll, destruction of houses and infrastructure, the surface tear, and the effects of the earthquake. Yet, for others, it is a number designated by scientists, magnitude 7.8 (USGS, 2023), that describes the earthquake. This case study explores how we have described earthquakes from past to present, to help us better understand this phenomenon.