Now, how is it known that these craterlets were caused by seismic liquefaction and not by artesian conditions?

53. The answer to the question of whether a source was seismic is provided by the topographic setting of the prehistoric craterlets. Artesian conditions are highly improbable along the crest in this field setting. In addition, the observation that nearly all the craterlets formed on the upper portions of ancient beach ridges, and only few formed on the lower portions of the ridges, agrees with historic observations made during the earthquake of 1886.