Triggering of the 4th May 2018 Mw 7.0 Hawaii earthquake by dike intrusion

On 4^th May 2018, a Mw 7.0 earthquake struck the south flank of Kīlauea, Hawaii, where volcanic activities have aggravated since late April. To investigate the possible cause-and-effect relationship between the magma movement and this earthquake, we have determined a co-seismic slip model based on geodetic, seismic and tsunami records and explored its relationship to the preceding stress evolution determined from modeling GPS time series from June 2012 to 20^th April 2018. The Kilauea and Mauna Loa summits inflated at 0.01 km³/yr, 0.005 km³/yr, respectively, over that time period forcing 25 cm/yr of seaward creep on the basal decollement beneath the southern flank of Mauna Loa. GPS and InSAR measurements from 20^th April to 4^th May 2018 imply opening by about 1m of a 45 km long dyke. The dyke extends from Makaopuhi Crater, where it lies at depth between 4 km and 8 km, to Leilani Estates, where it surfaces with fissure type eruptions. The magmatic inflation/diking and creep on the decollement resulted in a U-shaped zone of stress unloading, fringed by a zone of stress build up which guided the rupture during the Mw 7.0 earthquake.