A Look at Two Tsunamison the BC Coast with the Neptune-Canada Tsunami-meters A Look at Two Tsunamis on the BC Coast with the Neptune-Canada Tsunami-meters Richard Thomson (PI-IOS) Isaac Fine (Modelling-IOS) Alexander Rabinovich (Long Waves-IOS) Martin Heeseman (PGC) Earl Davis (PGC) Maxim Krassovski (IOS) NEPTUNE Science DMAS Team Steven Mihaly (IOS)

BPR (Bottom Pressure Recorders) PGC in collaboration with Bennest Enterprises developed a novel way to process data from Paroscientific Digiquartz pressure sensors substantially enhancing pressure resolution. This, along with the Cabled observatory enabled high temporal resolution gives us an unprecedented look at both seismic and oceanic waves in real-time 1 sec sampling, 0.4Pascal (~0.04mm ocean depth), 5microK. DART: 15min -> 15s acoustic modem-> satellite NEPTUNE TSUNAMIMETER 3 BPR array in 2600m surrounding the BPR at ODP Borehole 1026; the NE leg not deployed. ODP 889: 1260m Barkley Upper Slope: 400m Folger Deep: 100m Failed: Folger 27-Nov; NW 21-Feb

Samoan Earthquake Chilean Earthquake 200 km south of the Samoan IslandsOffshore Maule, Chile Tuesday, September 29, 2009, 17:48:11 UTC Saturday, February 27, 2010, 06:34:14 UTC M w =8.0 (indicating 1/16 th of the energy released in the Chilean earthquake) M w =8.8 (6 th strongest Earthquake since 1900, highest Tsunami wave energy in Pacific since 1964) Tsunami travelled 8300km to arrive at the Neptune array 11 hours later, averaging 755km/h Tsunami travelled 10,650km to arrive at the Neptune array 16 hours later, averaging 666km/h Well defined narrow band (9-13min) wavetrain with trough to crest height ~5cm Broad band wave energy (5-150min) max trough to crest wave height ~6cm Major Tsunamigenic Earthquakes in the Pacific since Deployment

Northwest BPR CORK BPR South BPR SAMOAN TSUNAMI Primary arrival consisted of 4 ~5cm waves with decreasing times between wave crests of 12min 50s, 10min 54s and 9min 54s, following waves were reduced to 2-3cm. With waves traveling in this direction the arrival times at the array nodes were only separated by ~30s - 1min. The third leg arrival time would be 4.5min later and thus greatly improve accuracy. It would also enable error estimation, or possibly test the plane wave assumption. Using the three BPR array and shallow water wave dynamics, wave characteristics could be estimated. (100km wavelength travelling 170km/h at 56 deg azimuth) 10km BPR Antenna

IOS Regional Tsunami Numerical Model Driven by the BPR tsunami data; model initialized using the first observed tsunami waves transposed to the boundaries A no-frills model optimised by Isaac Fine to run quickly based on the linear shallow water equations Grid spacing 180m x 160m, very sensitive bathymetric accuracy 140km 120km 80km Neptune-Canada BPR array Comparison between observations and model Data Model 38 min 26 min 20 min cm

CHILEAN TSUNAMI DATA (DMAS Related Issues) Improvements: most BPRs were recording, so that pre-event pressure spectra can be generated; seismic waves were recorded. Demerits: array no longer functional, NW BPR stopped recording 6 days prior to the event, giving rise to less accurate wave representation for the Regional Tsunami model; data gaps greatly affect processing WAVE CHARACTERISTICS Marginally larger (6 cm amplitude) waves compared to Samoan tsunami; ringing for half a day. Elevated energy for at least 3 days Complex Wave train with wave groups of 5-6, 9-13 min (as in Samoan) waves superposed on much longer min waves decibar Pre-event wave energy Seismic energy 140min 4.5h data gap resulting in unreliable data for ~day 10 Day Section of Tide-removed filtered pressure from BPR 1026 S 18h Zoom from 27-Feb 20:46:43 to 28-Feb 14:36:46, 2010

IOS Regional Tsunami Model Both the complexity of the wave and the loss of BPRs in the array limited our ability to extrapolate the observed pressure at 1026B to a wave at the model boundaries The modelled tsunami has spatially variable skill such that one pressure record at neighbouring pairs can be well represented whereas the other not; likely a result of inaccurate bathymetry.

Port Alberni (eigenfreq=120min) Comparison of the two Tsunamis at Tidal Stations Although open ocean wave heights for the two events were similar, the coastal responses were functions of the specific features of the two tsunamisAlthough open ocean wave heights for the two events were similar, the coastal responses were functions of the specific features of the two tsunamis Vertical Scale 3:1 50 cm Prince Rupert The BC coast acts as an active “transfer function” for incoming tsunami waves Note: no data gaps in 20 records! 150min 25 min 120min 50min 110min

FIN