The optimal placement of tsunameters in the Tasman Sea

TLDR: In the early 1990s, the Australian Bureau of Meteorology (BOM) deployed two bottom pressure recorders (BPRs) on the seafloor to detect tsunamis in the Tasman Sea as mentioned in this paper.

Abstract: An essential element in the provision of tsunami warnings is the ability to detect tsunamis through changes in sea level. This is important because not all earthquakes cause tsunamis, even those occurring along subduction zones, where tsunamigenic earthquakes are most likely to occur. Furthermore, it is not currently possible to determine in real time, from seismic data alone, whether an earthquake has generated a tsunami or not. There are a number of possible instruments that can be used for observing tsunamigenerated sea-level variability, such as coastal radars (e.g. Heron et al. 2008) and satellite altimeters (Ablain et al. 2006). The two main techniques used operationally within the Australian region for the detection of tsunamis are coastally based tide gauges and open-ocean-based tsunameters. A tsunameter consists of a bottom pressure recorder (BPR) installed on the sea floor, in deep water (typically deeper than 3000 m) which communicates via an acoustic link with a moored surface buoy. The BPR records pressure at fifteensecond intervals which is then converted to a change in sea surface height, with a precision of one millimetre (Meinig et al. 2005). As part of the Australian Tsunami Warning System project, the Australian Bureau of Meteorology (the Bureau) significantly expanded its sea-level observing network, including a mix of tide gauges and tsunameters. Two tsunameters were initially deployed in the Tasman Sea. These were placed in order to detect and provide warning guidance for tsunamis caused by earthquakes on the Puysegur subduction zone, located to the southwest of New Zealand (see Fig. 1). Over the past 25 years, there have been six earthquakes in this region with magnitudes over Mw = 6.0. These earthquakes occurred in 1988 (Mw 6.7), 1989 (Mw 6.4), 1993 (Mw 7.0), 2000 (Mw 6.1), 2003 (Mw 7.2) and 2009 (Mw 7.8) (Uslu et al. 2011). For the initial deployment of the tsunameters, both were placed near a single location deemed to be ‘optimal’, with a separation of approximately 70 km (Greenslade 2007). There were a number of reasons for placing them near each other. Firstly, and predominantly, one of the tsunameters was an experimental Easy-To-Deploy Deep-ocean Assessment and