Investigating the Past 100 Years of Fault Zone Deformation and Coulomb Stress Changes of Kilaueas Decollement

Kilauea Volcano on the Big Island of Hawaii is host to a complex volcanic and interwoven fault system. The decollement underlying its south flank has a high hazard potential and science interest due to the wide range of seismic events that have occurred along it, including large magnitude earthquakes, continuous creep, and slow slip events. The complexity of this region thus leads to important questions related to how the deformation and seismic cycle of the Kilauea region have evolved throughout time. The 1975 Mw7.7 Kalapana decollement earthquake is of particular interest because large magnitude ruptures can dramatically alter the state of stress within a region. We therefore explore both the deformation and stress changes of Kilaueas decollement from 1898-2018 by collating a wealth of geodetic data products, incorporating triangulation, trilateration, and leveling data, as well as GNSS, and offshore pressure sensor observations. An analytical model was created to examine the deformation prior to and after the 1975 Kalapana earthquake to determine what major features (i.e., rifts, dikes, magma chambers) and ranges of fault zone deformation parameters (slip, locking depth, volume, etc.) adequately predict the observed motion at Kilauea during these time periods. The significant model features were identified using a 5-fold cross validation method, while the parameter suite of the chosen features were selected via probability density functions. Close inspection of the model fit to the different geodetic data types reveals several key observations: (1) distinctive persistent characteristics, such as evolving locked zones, are prevalant along the decollement, (2) slip parameters are heavily time dependent and (3) temporal deformation rate changes are strongly linked to the seismic cycle of the 1975 Mw7.7 Kalapana earthquake. Our results give a unique insight into the buildup and aftermath of a major event seismic event at the still-active region of Kilauea and also provide an overview of its current state of stress and deformation. Moreover, consideration of Kilaueas complete geodetic history has important implications for improving our understanding of the mechanical and dynamical relationship between magmatic processes and earthquake cycle deformation transients.