Collaborative Research: Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip (HOBITSS)

在新西兰北岛俯冲带的Hikurangi部分部署一个压力计和地震仪网络，旨在记录预计在2014-2015年期间发生在板块边界断层上的慢滑事件（SSE）。在该地区，SSE每18个月发生一次，因此记录与这种类型的事件相关的变形，并将几周的活动与持续的微震活动进行比较，应该可以说明该地区的力量和相关危害的演变。 20个美国海底仪器，包括OBSIP的10个，将与类似数量的日本仪器组合使用约12个月。在这一国际合作中，这些数据将与陆上大地测量和地震台站的数据一起进行评估。结果将为未来可能的IODP海底钻探和后续原位测量提供规划。由于俯冲板块的浅倾角，Hikurangi站点提供了一个独特的机会来记录与SSE相关的小信号，对于人类感知来说，运动太小了。对这种新认识的板块相互作用模式的深入了解，预计将适用于其他收敛边缘。在目前对地震和海啸危险的估计中，“向上倾斜”的滑动延伸多远，是否一直延伸到俯冲海沟附近的海底，是一个关键的未知数。缓慢滑动的程度可以表明板块边界断层上的应力减轻了多少，而不是朝着最终的大逆冲地震积累。

Deployment of a network of pressure gauges and seismometers on the Hikurangi portion of the subduction zone off North Island New Zealand is designed to record a slow-slip event (SSE) expected to occur on the plate boundary fault in the 2014-2015 timeframe. SSE occur every ~18 months in this region, so documenting the deformation associated with this type of event and comparing that couple-week activity with ongoing microseismicity should illustrate the evolution of forces and associated hazards in this region. Twenty US seafloor instruments, including 10 from OBSIP, will be combined with a similar number of Japanese instruments for ~12 months. These data will be evaluated together with data from onshore geodetic and seismic stations in this international collaboration. Results will inform planning for possible future seafloor drilling by IODP and subsequent in-situ measurements.Due to the shallow dip of the subducting plate, the Hikurangi site offers a unique opportunity to document the small signals associated with SSE, for which motion is too minor for human perception. Insights into this newly-recognized mode of plate interaction are expected to be applicable to other convergent margins. How far 'up-dip' the slip extends, whether all the way to the seafloor near the subduction trench or not, is a key unknown in current estimates of earthquake shaking and tsunami hazard. The extent of slow slip can indicate how much stress on the plate boundary fault is relieved versus building up toward an eventual megathrust earthquake.