*Special Tuesday Seismo Lab Brown Bag Seminar

One of the central projects pursued in the first four decades of research at SeismoLab was the quantification of "earthquake size." For that purpose, Richter's landmark 1935 paper introduced the notion of "magnitude", which Gutenberg and him subsequently aimed to extend to earthquakes recorded at teleseismic distances and with variable focal depths. I will present an informal introduction to a comparative research project on quantitative measurement, in which the development earthquake magnitude plays a central role. Still today, most of the methodological writings on measurement across philosophy of science, mathematics, and the human and behavioural sciences rely on examples from experimental physics (thermometers, balances, clocks, etc.) to define what ‘proper' measurement ought to look like. Yet, most sciences cannot study more complex phenomena that cannot be decomposed under the controlled conditions of the physical laboratory. The history of quantification in seismology – starting with Richter and culminating in the moment magnitude scale – gives us a better understanding of the nature, prospects, and limits of quantitative measurement outside of experimental physics.