the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Dec 2025
Modeling tsunami and seismic waveforms from regional earthquakes to inform system design and data integration for the Tamtam SMART subsea cable
Abstract. Science Monitoring And Reliable Telecommunications (SMART) subsea cables utilize sensors integrated within repeaters to record temperature, acceleration, and pressure on the seafloor. The planned Tamtam SMART cable will connect Vanuatu and New Caledonia across a major subduction zone. Modeling recent MW 7.7 to 8.0 earthquakes and maximum considered MW 8.33 to 8.8 scenarios provides a range of seismic waveforms with realistic relative timing and long-period ground displacements at the sensor locations as well as coseismic seafloor uplift and subsidence at the sources used for tsunami excitation. A nonhydrostatic model describes tsunami generation, propagation, and scattering in the southwest Pacific. Spectral analysis of the computed tsunami waves shows multi-scale oscillations along the Vanuatu trench with periods from a few minutes to over an hour. The cable sensor locations are outside energetic antinodes of oscillation modes and the modeled tsunami amplitude is representative of the seismic source with minor interference from land masses. The suite of synthetic seismic and tsunami waveforms informs implementation of the sensor system for regional hazard monitoring. The Tamtam SMART cable, deployed in a very active tectonic environment with limited on-land instrumentation, will augment rapid earthquake and tsunami warning as well as source quantification.
- Preprint
(3687 KB) - Metadata XML
- BibTeX
- EndNote
Status: final response (author comments only)
-
CC1: 'Comment on egusphere-2025-5825', Charlotte Rowe, 09 Apr 2026
- AC1: 'Reply on CC1', Kwok Fai Cheung, 29 Apr 2026
-
CC2: 'Comment on egusphere-2025-5825', Laurent Foulonneau, 11 May 2026
Dear Kwok Fai, Matt, Bruce, and co-authors,
We have now had the opportunity to review the manuscript concerning the TamTam SMART cable project currently under discussion.
First, we would like to say that we appreciate the broader scientific objectives of the paper and the important work being done to advance understanding of how SMART cable systems can support hazards monitoring and ocean science applications in the Pacific region. We strongly support the scientific collaboration surrounding these efforts.
At the same time, we believe several portions of the manuscript require clarification and correction in order to accurately reflect the governance, financing, implementation structure, and operational data architecture of the TamTam project.
These issues are important not only from an institutional perspective, but also for ensuring that the scientific and technical record accurately reflects the operational structure of the project and the provenance and governance of the associated data systems.
In particular, we would respectfully request revisions in the following areas:
- Project Leadership and Implementation Structure
The current manuscript does not accurately reflect the role of Pacific Peering in leading and implementing the TamTam SMART cable project.
As presently written, readers could reasonably conclude that the project is principally organized and operationally managed through downstream scientific and monitoring institutions. This does not align with the actual implementation structure of the project.
We believe the manuscript should explicitly acknowledge Pacific Peering’s role in the leadership, implementation, operational coordination, and management of the SMART cable project infrastructure.
- French Financing and Institutional Contributions
The manuscript also does not sufficiently reflect the central role played by the French teams and French financing institutions in supporting and enabling the TamTam project.
The TamTam project is being financed France2030, with Ifremer serving as a central institutional partner in the implementation and operational management of the project.
Given the significance of these contributions to the realization of the project, we believe the manuscript should more clearly acknowledge the role of the French partners, including Ifremer and associated French-supported project structures.
- Data Governance and Operational Architecture
We are particularly concerned that the manuscript currently describes a data flow architecture that does not accurately reflect the operational design of the system.
The manuscript currently states:
“The collected data from the Tamtam SMART cable will be provided via ASN’s Climate Change Portal for low-latency distribution to hazards monitoring agencies [...] and for long-term storage and dissemination for further analysis and climate research via Ifremer [...]”
This description creates confusion regarding the governance, management, processing, and dissemination structure of the data.
As currently designed, SMART cable data associated with the TamTam project will first be transmitted to and managed through Ifremer, which serves as the central institutional manager of the data infrastructure. The data is managed and processed through Pacific Peering’s PPSP platform infrastructure, which is responsible for data management, processing, storage, access governance, and controlled distribution to relevant stakeholders, monitoring agencies, and scientific users.
We therefore request that the manuscript be revised to more accurately reflect the actual operational and governance structure of the project’s data systems and associated institutional responsibilities.
- Distinction Between Scientific Utilization and Project Governance
We also believe it is important for the manuscript to distinguish between:
- the organizations responsible for financing, implementing, operating, and governing the project infrastructure and associated data systems; and
- the scientific and research organizations that may subsequently utilize the data for hazards monitoring, scientific analysis, and climate research purposes.
These are complementary but distinct roles, and the manuscript currently conflates aspects of these functions in ways that may create confusion for external readers.
To assist constructively, we would be happy to provide proposed replacement language or additional technical clarification if helpful.
As these issues relate directly to the accuracy of the public scientific discussion record, we intend to submit formal comments through the journal discussion platform as part of the open review process.
We appreciate your attention to these concerns and hope these clarifications can be incorporated constructively as the manuscript moves through review.
Best regards,
Laurent FOULONNEAU
Pacific Peering
www.pacific-peering.comCitation: https://doi.org/10.5194/egusphere-2025-5825-CC2 -
RC1: 'Comment on egusphere-2025-5825', Anonymous Referee #1, 11 May 2026
The manuscript presents numerical simulations of seismic and tsunami signals at the planned Tamtam SMART cable. The study considers recent large regional earthquakes and UNESCO-IOC maximum scenarios, and extracts synthetic waveforms at the proposed cable sensor locations. Overall, the manuscript is a useful scenario-based study for a planned observing system.
The numerical schemes are generally well justified and clearly presented. The use of finite fault slip models, NEOWAVE-based tsunami modeling, and synthetic seismic wave modeling is appropriate for the purpose. However, these numerical approaches are already well established and widely used in tsunami and seismic-wave studies. Therefore, the manuscript could be made more concise in the methodological description and in the presentation of the numerical results.
Since the cable is not yet installed, direct validation against SMART-cable observations is not possible at this stage. This is understandable, but the limitation should be stated more explicitly. The authors should also discuss how the modeled signals could be validated after deployment, using future cable pressure and seismic records, as well as comparisons with tide gauges, DART stations, and regional seismic observations. This would help clarify how the present synthetic results may be tested and refined in the future.
The title refers to “information system design and data integration,” but these aspects need to be discussed more specifically. For example, the manuscript could discuss expected data specifications, including sampling rate, data volume, bandwidth, transfer latency, buffering, and real-time processing requirements. These are important for hazard mitigation because the practical value of the observations depends not only on detecting seismic or tsunami signals, but also on transferring and processing them fast enough for warning decisions.
The data-integration discussion would also benefit from more detail. At present, it appears to describe mainly future data distribution. The authors should explain more clearly how SMART-cable observations will be combined with tide-gauge, DART, seismic-network, and other observational data streams. For example, it would be useful to describe how cable seismic records may contribute to rapid source characterization, and how pressure records may contribute to tsunami confirmation, forecast, or warning timing.
Citation: https://doi.org/10.5194/egusphere-2025-5825-RC1 -
CC3: 'Comment on egusphere-2025-5825', Laurent Foulonneau, 13 May 2026
Dear authors,
As a follow-up to our previous community comment (CC2), we would like to draw attention to an additional technical point that we believe is important for readers to understand correctly.
Throughout the manuscript, the CC-Node positions are treated as fixed and established reference locations — most explicitly through the designation of a target location at (18.782°S, 168.2°E) for sensor 2, which serves as the basis for all seismic and tsunami waveform modeling (line 187: _"Dynamic ground motions are computed at a target location (18.782°S, 168.2°E), which is planned for sensor 2 on the Tamtam SMART cable"_), and from which operational conclusions are directly drawn (line 315: _"At least one SMART sensor will be located within the tsunami source regions of subevents A through C"_). At no point does the manuscript acknowledge that these coordinates represent a preliminary and theoretical cable route.
We would also like to ask the authors to clarify the sources from which the CC-Node positions used in this manuscript were obtained. As the operator of the TamTam SMART cable project, Pacific Peering has not been consulted regarding the use of any positional data in this manuscript, and we are not aware of any publicly available source from which these coordinates could have been legitimately derived.
Furthermore, the positions of the CC-Nodes have already been subject to revision based on cable risk assessment and technological constraints. As of the date of this comment, the marine survey has not yet taken place and the Route Position List (RPL), which will define the final CC-Node positions, has not yet been established. The actual sensor positions are therefore currently unknown, and will potentially be refined again once the marine survey and route design process are completed.
We therefore suggest that the publication of this manuscript be delayed until the final CC-Node positions have been confirmed. Positional information will be made available in due course by Ifremer, which leads and manages the scientific aspects of the TamTam SMART cable project.
Laurent Foulonneau
www.pacific-peering.comCitation: https://doi.org/10.5194/egusphere-2025-5825-CC3 -
RC2: 'Comment on egusphere-2025-5825', Anonymous Referee #2, 13 May 2026
The manuscript presents a comprehensive, technically rigorous modelling study of seismic and tsunami signals expected along the planned Tamtam SMART subsea cable between Vanuatu and New Caledonia. It integrates finite-fault rupture models, non-hydrostatic tsunami simulations, and synthetic long-period seismic waveforms to inform sensor design and hazard monitoring. The work is timely, regionally relevant, and methodologically sound, with clear implications for early warning and emergency management.
A strong, well‑structured, and impactful study that significantly advances the scientific and operational case for the Tamtam SMART cable. The modelling is robust, and the results are highly relevant for hazard monitoring. The main limitations relate to the simplified seismic structure, the lack of short-period motion analysis, the absence of uncertainty quantification and inundation. Addressing these would elevate the work to a fully comprehensive hazard‑assessment reference.
The paper clearly establishes the need for offshore instrumentation in a region with frequent MW 7.5+ earthquakes and limited on-land coverage. The combination of finite-fault slip models for historical and maximum scenarios, NEOWAVE non-hydrostatic tsunami modelling, and SYNGINE long-period seismic synthetics provides a multi-hazard, multi-scale view. The spectral analysis shows that the planned sensor sites lie outside energetic antinodes, ensuring clean tsunami recordings. The study provides arrival times, amplitudes, and spectral content for both seismic and tsunami signals, directly supporting VMGD and NDMO operational planning. The inclusion of three recent major events (2013, 2021, 2023), five MW 8.33 subevents, and a full MW 8.8 maximum scenario provides a broad parameter space for hazard assessment. The manuscript quantifies P-wave detection arrivals, surface-wave windows for magnitude estimation, and tsunami arrival times (~1 hour for distant events; 11–18 min for local sources). This is directly actionable for early warning system design.
Seismic modelling uses a 1D PREM-based model, which limits realism for path-dependent amplification, basin effects, and sediment-induced resonance. The authors acknowledge this but do not quantify potential biases. A 1‑D model assumes smooth, radially symmetric velocity gradients. The region contains thick sedimentary basins, volcanic arcs, subducting slabs and strong velocity contrasts across the trench. The use of a 1D PREM-based velocity model introduces predictable biases because it cannot account for the strong lateral heterogeneity of the Vanuatu subduction system. These include potential misestimation of ground‑motion amplitudes (±20–50%), arrival‑time errors (5–20 s for surface waves), incorrect surface‑wave dispersion, and the absence of basin or trench resonances that influence waveform duration and coda. The resulting synthetic seismograms are likely smoother and less complex than real observations, with underestimated high‑frequency energy and path‑dependent amplification. Quantifying these biases, even approximately, would strengthen the interpretation of seismic modelling results and clarify their implications for SMART cable sensor performance and early warning applications.
The study explicitly avoids predicting velocities/accelerations, yet these are critical for sensor survivability, on‑scale recording and sediment–structure interaction. Short-period ground motion (typically 0.1–10 Hz) controls peak ground acceleration (PGA) and peak ground velocity (PGV), which are the high-frequency shaking that can clip, saturate, or damage sensors. Without short‑period modelling, the magnitude of this interference is unknown. The manuscript models only long-period displacement (>15 s), which is too slow for early warning.
The modelling lacks sensitivity tests, parameter uncertainty bounds, and probabilistic outputs that provide hazard context. Add uncertainty and sensitivity analyses through slip distribution variability, rupture velocity, bathymetric perturbations and manning roughness sensitivity. Even a simplified 3-D model (regional tomography) would improve amplitude accuracy, arrival-time realism, and surface-wave dispersion.
Although the manuscript references the regional DART buoy network from New Zealand and the ORSNET land‑based seismic stations, these datasets are not used to validate or calibrate the synthetic tsunami or seismic waveforms. This omission is important because both datasets provide real observations of tsunami propagation, spectral content, and seismic waveforms in the region. Without even a basic comparison between synthetic and observed signals, the reader cannot assess the accuracy of the modelling framework, the realism of the assumed rupture parameters, or the reliability of the predicted amplitudes and arrival times at the SMART‑cable sites. Incorporating DART and land-seismic constraints—or, at a minimum, quantifying the expected mismatch—would substantially strengthen confidence in the synthetic results and their application to early-warning system design. The MW 8.8 scenario is hypothetical. Its credibility depends on showing that the modelling framework reproduces the 2013 MW 8.0, the 2021 MW 7.7 and the 2023 MW 7.7 events.
Without inundation modelling, the hazard interpretation for communities is incomplete. Even coarse inundation maps would strengthen the emergency‑management relevance.
Viewed
| HTML | XML | Total | BibTeX | EndNote | |
|---|---|---|---|---|---|
| 1,456 | 534 | 171 | 2,161 | 123 | 175 |
- HTML: 1,456
- PDF: 534
- XML: 171
- Total: 2,161
- BibTeX: 123
- EndNote: 175
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
First, I'd like to say what a pleasure it is to read a manuscript that is so well-written. So often this is not the case, and it makes it so easy to follow the technical aspects. I have only a few comments / requests regarding revision.
1) Line 33: As a seismologist, I feel compelled to mention one of my major concerns regarding the SMART sensors, that the seismic sensors should be seismometers (velocimeters), not accelerometers - or include both. Here in the introduction only acceleration is mentioned, although I see that much later in the manuscript where instruments are discussed, the authors do state that Alcatel is including both (phew!). Please be consistent. Perhaps you could say "seismic ground motions"
2) Line 55: a comma after "earthquakes" would improve clarity.
3) Figure 1: Great figure and combining the seismicity, bathymetry and nested computational grids is an efficient way to go - but it’s confusing to the reader to see mention of these grids and their levels without having been mentioned and defined in the text. Normally a figure does not appear before its contents have been referenced in the body of the manuscript. Is it possible to mention and define these grid levels before the figure appears, or, alternatively make an additional figure later in the manuscript that explicitly addresses them once they have actually been introduced to the reader? Also, grid lines are hard to see.
4) Line 81: I don't expect this to be addressed here, but I'm just curious if anyone has investigated Coulomb stress changes for the event pairs, and if the probabilities are consistent with the occurrences of secondary events.
5) Line 96: Another "just curious" - would the SMART cable deployment include sufficient slack to accommodate maximum anticipated displacements in the immediate vicinity (akin to the accommodation engineered into the Trans-Alaska Pipeline where it crosses major faults)?
6) Line 96: "SMART Cable would be located"
7) Lines 106-108: It seems like more references are needed here when calling out the different types of finite fault slip models, or is Yamazaki et al. intended to cover them all? I'd like to see some original works cited here.
8) Line 137: "long-periods" In the usage you have, it probably shouldn't be hyphenated (whereas short-periods is correct to be hyphenated since it serves as a single adjective) . The bigger question is that are you referring to spatial wavelength or temporal oscillations? In either case it would be nice to have a rough frequency defined, i.e., "with long periods (~20 s) consistent..."
9) Figure 2 caption: Slip distribution - total or vertical?
10) Line 150: modeling is made to capture the maximum scenario. For hazard planning this is prudent. Is there a most likely scenario?
Again, I really like this paper and my questions/comments amount to extremely minor changes.