Whose studies first explained the formation of fault scarps after earthquakes?

Fault scarps are steep steps in the landscape created when one side of a fault moves up or down relative to the other. Earthquake studies in the 20th century showed that such features can form suddenly during large quakes. Later work in seismology and geomorphology linked scarps to active faults and recurrence of movement over time. They are important because they show where the ground has broken before and may break again. Mapping fault scarps is now a standard part of earthquake hazard assessment.