Tsunami Detection by High Frequency Radar Using a Time-Correlation Algorithm: Performance Analysis Based on Data From a HF Radar in British Columbia
Bibliographic record
Abstract
A High-Frequency (HF) radar was installed by Ocean Networks Canada in Tofino, BC, to detect tsunamis from far-and near-field sources on the Pacific Ocean side of Vancouver Island; in particular, from seismic sources in the Cascadia Subduction Zone. Based on a classical analysis of the Doppler spectrum, this HF radar can measure ocean surface currents up to a 85-110 km range depending on sea state. However, an inherent limitation of detection of small and short-lived tsunami currents is the conflicting requirement for short integration time and sufficient accuracy (resolution) of the Doppler spectra. This limits a direct tsunami detection typically to shallow water areas over the continental shelf where tsunami currents have become sufficiently strong due to wave shoaling. To overcome this limitation, the authors have recently proposed a new detection method, referred to as "Time-Correlation Algorithm (TCA)", that does not require inverting Doppler spectra for the tsunami currents and can thus potentially detect an approaching tsunami in deeper water, beyond the continental shelf. This algorithm is based on computing space-time correlation of the raw radar signal in different radar cells aligned along precomputed tsunami wave rays, and time-shifted by the precomputed tsunami propagation time between cells. A change in pattern of such correlations indicates the presence of a tsunami. They validated the TCA with numerical simulations for both idealized (Grilli et al., 2016a) and realistic (Grilli et al., 2016b, 2017) tsunami wave trains and seafloor bathymetry, using data simulated with a radar simulator. Here, the TCA is for the first time applied to actual radar data measured with the ONC WERA HF radar and numerically modified by a synthetic tsunami current. Using a state-of-the-art long wave model we perform tsunami simulations with realistic source and bathymetry, and combine the resulting currents with the background currents and radar backscattered signal measured by the HF radar system. This combination makes it possible to evaluate the performance of the proposed TCA detection algorithm, based on an experimental rather than numerically simulated, data set of radar signal. Our findings confirm that an actual detection can be achieved beyond the continental shelf, where tsunami currents are small (as low as 5 cm/s), in deeper water than when using an algorithm based on a direct inversion of currents from the measured radar Doppler spectra.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".