Low-Frequency Earthquakes Accompany Deep Slow-Slip beneath the North
Island of New-Zealand
Abstract
Slow-Slip Events (SSEs) haven been observed along the Hikurangi
subduction zone of the North Island of New-Zealand. They occur both in
the shallow plate interface (<15km depth) and at the deeper
end of the seismogenic-zone (>30km depth). Some slow slip
events in New-Zealand are also accompanied by tectonic tremors, although
tremor is not as common at the Hikurangi subduction zone compared to
other subduction zones. We present a systematically generated catalog of
low-frequency earthquakes (LFEs) for the central Hikurangi margin. To
detect preliminary LFEs from the continuous seismic data we used a
Matched-Filter technique with template waveforms from the tectonic
tremor catalog of Romanet & Ide [2019]. The resulting detections
were gathered as families and an innovative stacking technique was used
to extract high-quality waveforms in order to build a set of LFE
templates for a second Matched-Filter search. From these second
generation detections, we developed a methodology to continuously scan
the entire dataset for coherent impulsive waveforms similar to LFE that
occuring on the subducting plate interface. The LFEs are organized into
episodes of intense activity during deep M7 SSEs that occur absit every
5 years beneath the Manawatu region. One of our LFE bursts occurs during
a small, deep SSE recognized at the central Hikurangi margin in 2008
(Wallace and Eberhart-Phillips, 2013). We expect that the other LFE
episodes highlight small slow transients that have not yet been
geodetically observed. In this presentation, we discuss the
spatiotemporal evolution of LFEs in regard to potential aseismic
transients that can be observed in the GPS data-set acquired by GeoNet.