Mechanics of inflationary deformation during Caldera collapse: Evidence from the 2018 Kīlauea Eruption

During the 2018 Kilauea eruption the caldera ffloor dropped 500 meters in 62 nearly periodic events of up to 8 meters. Caldera collapse maintains pressure in the magma reservoir necessary to sustain high-rate eruptions. The 2018 collapses were accompanied by inflationary tilts and displacements, similar to observations at other basaltic calderas. Collapse is modeled in 2D by uniform slip dislocations intersecting a magma chamber. Collapses occurred rapidly, such that mass within the chamber was constant. For vertical faults surface deformation outside the collapse results only from chamber pressurization with displacements anti-parallel to pre-collapse deflation, similar to observations. For inward dipping faults the predicted ratio of horizontal to vertical displacements during collapse is greater than for the pre-collapse deflation, as observed. For outward dipping faults the horizontal displacements are inward, contrary to data. The average deformation trends during the eruption depend on fault dip and whether stress required to trigger collapses was constant or changed with time.