11:00 AM - 11:15 AM
[SGD01-08] Gravity changes due to the 2016 Kaikoura earthquake
Keywords:Kaikoura earthquake, gravity changes, crustal movements, relative gravity measurements, absolute gravity measurements
Since the gravity changes due to the vertical crustal movements provide the information about the subsuface density changes, which would be usefull for considering the rupture mechanism, we have conducted relative gravity measurements at bench marks along State Highway 1 (SH1) from Blenheim to Christchurch. The obtained gravity values were compered with those of the 1980's precise gravity network. Although the uncertainties of the comparisons were not small, the results clearly show the gravity changes due to the widespread uplift. In particular, the gravity changes around Ward are significant and a step of the gravity change of about 0.5 mGal is clearly detected across the Kekerengu Fault.
In addition to the relative gravity measurements, we conducted absolute gravity measurments at 2 sites in Marlborough region in Sep. 2017, and we plan to reoccupy the same points in April-May 2018 to detect the possible gravity changes due to postseismic deformation. We also plan to conduct GNSS survey at the gravity bench marks to evaluate height changes more precisely. These data will be used to estimate the ratio between the gravity changes vs height changes, which should provide useful information about the mechanism of the crustal movements.
This study was partially supported by JSPS KAKENHI Grant No. 15H05205.