Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

S (Solid Earth Sciences ) » S-CG Complex & General

[S-CG61] Dynamics in mobile belts

Tue. May 28, 2019 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Toru Takeshita(Department of Natural History Sciences, Graduate School of Science, Hokkaido University), Hikaru Iwamori(Geochemical Evolution Research Program, Japan Agency for Marine-Earth Science and Technology)

[SCG61-P27] Precise hypocenter distribution in the focal area of the 2016 Mw7.8 Kaikorua Earthquake, New Zealand

*Yuta Kawamura1, Satoshi Matsumoto1, Tomomi Okada2, Miu Matsuno2, Yoshihisa Iio3, Tadashi Sato2, Stephen C Bannister4, John Ristau4, Martha K Savage5, John Twonend5, Jarg Pettinga6, Francesca Ghisetti7, Richard H Sibson8 (1.Kyushu University, Shimabara, Japan, 2.Tohoku University, Sendai, Japan, 3.Kyoto University, Uji, Japan, 4.GNS Science, Lower Hutt, New Zealand, 5.Victoria University of Wellington, Wellington, New Zealand, 6.University of Canterbury, Christchurch, New Zealand, 7.TerraGeologica, Ruby Bay, New Zealand, 8.University of Otago, Dunedin, New Zealand)

The Mw7.8 Kaikoura Earthquake struck the northeastern south island, New Zealand, on November 14, 2016. A lot of researchers have tried to explain the cause of this earthquake and revealed the structure in this area. Among variety of prior researches, Clark et al. (2017) argued that this earthquake, which produced surface deformation including uplift and complex surface rupture, was caused by 21 strike-slip, reverse and oblique slip faults. Cesca et al., (2017) proposed an earthquake fault model that consists of three faults in northern, central and southern part, based on the hypocenter distribution of aftershock activity. These studies suggested in common that this earthquake was provoked by multiple faults with complex rupture process.

We had installed 75 temporary seismic stations before the earthquake in the South Island, New Zealand in addition to GEONET stations. The seismic network has successfully recorded the mainshock and the following aftershocks. Here, we relocated the hypocenters of the events associated with the Kaikoura earthquake by using data obtained from the seismic network. The hypocenters was determined by the double difference hypocenter determination algorithm (i.e. HYPODD, Waldhauser and Ellsworth, 2000).
The overall distribution of the hypocenters are distinguished into two clusters, northern and southern clusters. The hypocenter distribution in vertical cross section normal to the major alignment of the aftershocks in N54W reveals that the fault in southern part dips to eastward. On the other hand, although we find out a northern cluster in terms of horizontal projection, no obvious faults are recognized in the vertical cross-section, suggesting complex fault structure in the northern cluster.