2:45 PM - 3:00 PM
[J02-3-05] Seafloor displacement of the 13 November 2016 New Zealand earthquake estimated from tsunami waveforms and GPS data
A large earthquake (Mw 7.8) occurred on 13 November 2016 at 11:02:56 UTC in North Canterbury, New Zealand. The earthquake initiated at 42.6925 S, 173.0221 E, and depth of 15 km beneath South Island. The earthquake has an oblique faulting mechanism and produced surface ruptures from multiple active faults. The aftershock area is 150 km long and 40 km wide and a part of it is located offshore. A large tsunami amplitude of 2.5 m was recorded at Kaikoura tide gauge and 5 cm to 50 cm were recorded at seven other tide gauges. The Kaikora tide gauge record also indicated a vertical uplift of 0.9 m. The vertical uplifts at KAIK and CMBL GPS stations which are located near the coast and within the source area are 0.4 and 1 m, respectively.
In this study, we used tsunami waveforms at four tide gauges (Castle point, Wellington, Kaikoura, and Christchurch) and the uplift data to estimate the seafloor displacement. We distributed 72 (18 x 4) B-spline function unit sources with spatial distance of 10 km. The resolution test show that the dataset can resolve well the displacement with 20 km of spatial variation anywhere in the offshore but the displacement with 10 km spatial variation can be resolved around the Kaikoura station.
The earthquake produced two distinct uplift regions within the aftershock area. The first region is located immediately northeast of Kaikoura and the second region is centered at approximately 70 km northeast of Kaikoura. Both seafloor uplift regions are peaked at about 1 m, and the uplift tends to become gradually smaller from the shoreline toward offshore. We interpreted that this displacement is generated by the combination of multiple active faults and an underlying thrust fault ruptures. Tsunami simulation produced tsunami amplitudes of more than 0.5 m along 200 km coastline and the maximum tsunami amplitude is 3 m. The tsunami propagation model shows that oscillation of water body occurred locally near the coastline within the tsunami source area.
In this study, we used tsunami waveforms at four tide gauges (Castle point, Wellington, Kaikoura, and Christchurch) and the uplift data to estimate the seafloor displacement. We distributed 72 (18 x 4) B-spline function unit sources with spatial distance of 10 km. The resolution test show that the dataset can resolve well the displacement with 20 km of spatial variation anywhere in the offshore but the displacement with 10 km spatial variation can be resolved around the Kaikoura station.
The earthquake produced two distinct uplift regions within the aftershock area. The first region is located immediately northeast of Kaikoura and the second region is centered at approximately 70 km northeast of Kaikoura. Both seafloor uplift regions are peaked at about 1 m, and the uplift tends to become gradually smaller from the shoreline toward offshore. We interpreted that this displacement is generated by the combination of multiple active faults and an underlying thrust fault ruptures. Tsunami simulation produced tsunami amplitudes of more than 0.5 m along 200 km coastline and the maximum tsunami amplitude is 3 m. The tsunami propagation model shows that oscillation of water body occurred locally near the coastline within the tsunami source area.