two plots show summit tilt and seismicity

These two plots show summit tilt (ground deformation) and seismicity (earthquake counts) on Kīlauea Volcano between July 15 and August 5, 2018. A regular pattern emerged in which seismicity gradually increased over 1-3 days (bottom), until the caldera floor suddenly dropped several meters (yards) in a matter of seconds. The sharp upward steps on the tilt plot (top) reflect when these summit collapses occurred, causing the ground outside the collapsing area to rebound.