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- The contribution of submarine optical fiber telecom cables to the monitoring of earthquakes and tsunamis in the NE AtlanticPublication . Matias, Luis; Carrilho, Fernando; Sá, Vasco; Omira, Rachid; Niehus, Manfred; Corela, Carlos; Barros, José; Omar, YasserRecent developments in optical fiber cable technology allows the use of existing and future submarine telecommunication cables to provide seismic and sea-level information. In this work we study the impact of three different technologies, 1) SMART, Science Monitoring and Reliable Telecommunications; 2) DAS, Distributed Acoustic Sensing, and; 3) LI, Laser Interferometry, for effective earthquake and tsunami monitoring capabilities on the NE Atlantic. The SW Iberia is the source area of the largest destructive earthquake that struck Europe since the year 1000, the November 1, 1755 event. This earthquake generated also a destructive tsunami affecting the whole basin. This tectonically active area is crossed by the CAM (Continent-Azores-Madeira) submarine cable on a ring configuration. Due to the end of cable lifetime the current cables need to be replaced by 2024 and the technical requirements must be defined in mid-2021. The Azores archipelago is the focus of frequent seismic crizes and occasionally destructive earthquakes. A common feature of these seismic events is that they take place offshore, an area that is difficult to monitor from land-based instruments. In this work we evaluate the contribution of SMART cables to the earthquake monitoring and tsunami early warning system in SW Iberia and show how DAS and LI can improve earthquake monitoring on two active domains of the Azores. For tsunami early warning, we show how the offshore sea-level measurements provide clean offshore tsunami records when compared to coastal observations by tide gauges, which greatly improves the efficiency of the system. For earthquake monitoring, the data processing operational routine is examined using Monte-Carlo simulations. These take into consideration the errors in phase picking and the uncertainty on the 1D velocity model used for earthquake location. Quality of earthquake location is examined using the difference between the true location and the centroid of the computed epicenters and by the overall ellipse of uncertainty obtained from 100 runs. The added value provided by instrumented submarine telecommunication cables to mitigate earthquake and tsunami risk demonstrated in this work will help authorities and the society in general to take the political decisions required for its full implementation worldwide.
- Insight on the crustal stress state in Faial and Pico Islands (Azores), from analysis of aftershocks of the 1998 earthquakePublication . Dias, Nuno; Tellez, Julia; Matias, LuisThe seismicity in the Azores plateau can be of volcanic or tectonic origin, the latter usually more destructive, especially in the central group of islands. In this study we aimed to obtain crustal stress indicators from seismic data collected in July 1998, following the July 9th M5.8 earthquake that struck near Faial and Pico islands. The maximum horizontal stress (SHmax) azimuth was obtained from two methods. For the seismogenic volume, the SHmax was obtained from single and composite focal mechanisms, whereas the state of stress beneath the seismic network was derived from shear-wave splitting analysis of local earthquakes. The composite focal mechanisms were obtained from a waveform clustering method applied to identify "identical" earthquakes. The seismic anisotropy analysis could be applied to only six stations, the polarization of the first S arrival being stable, and with a secondary perpendicular pulse arriving 0.6-0.24 s later. The focal mechanisms provided a NW-SE SHmax with azimuth range of 96 degrees-114 degrees, and an associated transition of normal-fault to strike-slip dominant regime consistent with the estimated regional field of 110 degrees-120 degrees, and coherent with movement along three fault systems. Inland the SHmax azimuths present greater variability. In Faial, the stations located north of the Caldeira present a stable azimuth of 151 degrees-153 degrees and are consistent with the effect of a NNW-SSE fault system present in the islands, rotating to 50 degrees-77 degrees in the eastern sector of the Pedro Miguel Graben, probably due to a complex interaction of the WSW-ENE dominant fault system with old eroded volcanic complexes that segmented the island into several blocks. In Pico island, the SHmax direction azimuth ranges from 93 degrees to 135 degrees, in a radial pattern around the island's main stratovolcano, overlapping the regional stress field.
- The making of the NEAM Tsunami Hazard Model 2018 (NEAMTHM18)Publication . Basili, Roberto; Brizuela, Beatriz; Herrero, Andre; Iqbal, Sarfraz; Lorito, Stefano; Maesano, Francesco Emanuele; Murphy, Shane; Perfetti, Paolo; Romano, Fabrizio; Scala, Antonio; SELVA, Jacopo; Taroni, Matteo; Tiberti, Mara Monica; Thio, Hong Kie; Tonini, Roberto; Volpe, Manuela; Glimsdal, Sylfest; Harbitz, Carl Bonnevie; Lovholt, Finn; Baptista, Maria Ana Carvalho Viana; Carrilho, Fernando; Matias, Luis; Omira, Rachid; Babeyko, Andrey; Hoechner, Andreas; Gurbuz, Mucahit; Pekcan, Onur; Yalciner, Ahmet; Canals, Miquel; Lastras, Galderic; Agalos, Apostolos; Papadopoulos, Gerassimos; TRIANTAFYLLOU, IOANNA; Benchekroun, Sabah; Jaouadi, Hedi Agrebi; Ben Ahmed, Samir; Bouallegue, Atef; Hamdi, Hassene; Oueslati, Foued; Amato, Alessandro; ARMIGLIATO, ALBERTO; Behrens, Joern; Davies, Gareth; Di Bucci, Daniela; Dolce, Mauro; Geist, Eric; GONZALEZ-VIDA, J.M.; Gonzalez, Mauricio; Macías, Jorge; Meletti, Carlo; Sozdinler, Ceren Ozer; Pagani, Marco; Parsons, Tom; Polet, Jascha; Power, William; Sorensen, Mathilde; Zaytsev, AndreyThe NEAM Tsunami Hazard Model 2018 (NEAMTHM18) is a probabilistic hazard model for tsunamis generated by earthquakes. It covers the coastlines of the North-eastern Atlantic, the Mediterranean, and connected seas (NEAM). NEAMTHM18 was designed as a threephase project. The first two phases were dedicated to the model development and hazard calculations, following a formalized decision-making process based on a multiple-expert protocol. The third phase was dedicated to documentation and dissemination. The hazard assessment workflow was structured in Steps and Levels. There are four Steps: Step-1) probabilistic earthquake model; Step-2) tsunami generation and modeling in deep water; Step-3) shoaling and inundation; Step-4) hazard aggregation and uncertainty quantification. Each Step includes a different number of Levels. Level-0 always describes the input data; the other Levels describe the intermediate results needed to proceed from one Step to another. Alternative datasets and models were considered in the implementation. The epistemic hazard uncertainty was quantified through an ensemble modeling technique accounting for alternative models' weights and yielding a distribution of hazard curves represented by the mean and various percentiles. Hazard curves were calculated at 2,343 Points of Interest (P01) distributed at an average spacing of -20 km. Precalculated probability maps for five maximum inundation heights (MIH) and hazard intensity maps for five average return periods (ARP) were produced from hazard curves. In the entire NEAM Region, MIHs of several meters are rare but not impossible. Considering a 2% probability of exceedance in 50 years (ARP approximate to 2,475 years), the POIs with MIH >5 m are fewer than 1% and are all in the Mediterranean on Libya, Egypt, Cyprus, and Greece coasts. In the North-East Atlantic, POIs with MIH >3 m are on the coasts of Mauritania and Gulf of Cadiz. Overall, 30% of the POIs have MIH >1 m. NEAMTHM1 8 results and documentation are available through the TSUMAPS-NEAM project website (http://www.tsumaps-neam.eu/), featuring an interactive web mapper. Although the NEAMTHM1 8 cannot substitute in-depth analyses at local scales, it represents the first action to start local and more detailed hazard and risk assessments and contributes to designing evacuation maps for tsunami early warning.
- The Portuguese national seismic network: products and servicesPublication . Carrilho, Fernando; Custodio, Susana; Bezzeghoud, Mourad; Oliveira, Carlos; Marreiros, Célia; Vales, Dina; Alves, Paulo; Pena, Areosa; Madureira, Guilherme; Escuer, Maria; Silveira, Graça; Corela, Carlos; Matias, Luis; Silva, Matilde; Veludo, Idalina; Dias, Nuno; Loureiro, Afonso; Borges, J. F.; Caldeira, Bento; Wachilala, Piedade; Fontiela, JoaoPortugal, located in the southwest region of the Eurasian plate, has been affected by several destructive earthquakes throughout its history, the most well-known being the 1755 Great Lisbon earthquake. The seismicity of the territory, both in the mainland and in the Azores and Madeira islands, has prompted the continuous development of seismic monitoring, from the first known macroseismic inquiry, following the 1755 Great Lisbon earthquake, to the current state-of-the-art seismic network. Once scattered in separate efforts, at present, most seismic stations in Portugal relay its data to a common data center, at Instituto Português do Mar e da Atmosfera, where data are automatically processed for the downstream generation of both manually revised and automatically generated products and services. In this article, we summarize the evolution of the permanent seismic network, its current status, the products and services that are publicly available, a recent effort of rapid deployment of a dense network following a mainshock, and state-of-the-art ocean-bottom seismometer developments.