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

在新西兰北岛外俯冲带的Hikurangi部分部署了压力计和地震仪网络，旨在记录预计在2014-2015年间在板块边界断层上发生的慢滑事件。SSE在该地区每隔18个月发生一次，因此记录与这类事件有关的形变，并将这两周的活动与正在进行的微震活动进行比较，应该可以说明该地区力量和相关灾害的演化。20台美国海底仪器，包括10台来自OBSIP的仪器，将与类似数量的日本仪器相结合，为期约12个月。在这项国际合作中，这些数据将与陆上大地测量站和地震台的数据一起进行评估。由于俯冲板块的浅倾角，Hikurangi遗址提供了一个独特的机会来记录与SSE有关的小信号，对于这种小信号来说，人类感觉不到运动太小。对这种新认识的板块相互作用模式的洞察，预计也适用于其他收敛的边缘。在目前对地震和海啸风险的估计中，滑移向上延伸了多远，无论是否一直延伸到俯冲海沟附近的海底，这是一个关键的未知因素。缓慢滑动的程度可以表明，相对于最终发生大地震，板块边界断层上的应力得到了多少缓解。

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.