Primary evidence includes clues that are created by the movement on the fault during the earthquake such as fault scarps, offset or folded layers of sediment and soil, and parts of the landscape that have been tilted, uplifted, down-dropped, or torn apart.The picture above shows an example of a fault scarp from the relatively small 2014 South Napa earthquake (M6.0). For example, a historic account from the 1857 M7.9 earthquake on the San Andreas Fault in southern California, stated that “This rent was in some places 5-10 yards wide, the earth at times filling it up like ploughed furrows; at others the ground stood apart, leaving a deep fissure.” Secondary evidence includes clues produced by the shaking during the earthquake such as sand blows, rockfalls, landslides, and damaged trees.The use of lidar (See Down in the Trenches and Up in the Air) in geological investigations has made it much easier to map active faults.
Earth scientists can gather data at key sites along sections of a fault to figure out the past timeline of earthquakes at each spot.What methods do they use and how do these methods work?In this article, we will examine the methods by which scientists use radioactivity to determine the age of objects, most notably carbon-14 dating.This type of research is called paleoseismology (“paleo&Close Curly Double Quote; means old, and “seismology&Close Curly Double Quote; is the study of earthquakes, so paleoseismology is the study old earthquakes).
The basic assumption that paleoseismologists use is that what happened in the past will most likely happen again in the future.
Archaeologists now have new tools for studying the development of medieval villages and the transformation of the historical landscapes surrounding them. Radiocarbon dating is a key tool archaeologists use to determine the age of plants and objects made with organic material.