Funding:

Project Acronym: PT-AQUASEIS

Project Name:  monitoring the PorTuguese AQUifers with Ambient SEISmic noise interferometry

Activity years: 2025 - 2028

Funding: Fundação para a Ciência e a Tecnologia, I.P, na sua componente de Orçamento de Estado

Topic: Earth and Related Environmental Sciences – Geophysics

Budget: 249.998,40€

Reference:  2023.17310.ICDT

DOI: https://doi.org/10.54499/2023.17310.ICDT

Host Institution: Instituto Superior de Engenharia de Lisboa (ISEL)

Partners: Associação para a Investigação e Desenvolvimento de Ciências (FCiências.ID); Universidade do Algarve (UAlg).

Principal Investigator:

Maria da Graça Medeiros da Silveira CienciaID 1116-1080-16F3;  ORCID 0000-0002-2110-2554

Researchers (ISEL):

Alexandra Afilhado ORCID 0000-0003-0256-8540

David Schlaphorst ORCID 0000-0001-9959-7393

Joana Alves Ribeiro ORCID 0000-0001-8491-3904

Nuno Afonso Dias ORCID 0000-0001-7672-4476

 

Description:

This project will leverage the Portuguese permanent seismic stations and previous temporary deployments, resulting in a comprehensive network comprising over 30 stations, to implement interferometry techniques for aquifer monitoring. To assess how these seismic techniques respond in Southern Portugal, we will validate the results in one of the well-studied aquifers in the Algarve. We will compare the seismic measurements with piezometric, InSar, GPS, and geolectric data.

Seismic waves exhibit variable speeds as they traverse diverse materials. Their transmission is intricately influenced by the mechanical properties of the medium they travel, encompassing density, elasticity, and fluid content. Significantly, heightened pore pressure within water-saturated rocks prompts the formation of cracks, thereby reducing intergranular contact and decreasing shear-wave velocity. Consequently, relative changes in seismic velocity associated with shifts in pore pressure offer valuable clues for estimating variations in groundwater content. This approach sheds light on processes such as charge and depleting aquifers driven by seasonal fluctuations or human activities [1, 2, 3]. This alternative analytical method facilitates a more comprehensive assessment of groundwater dynamics, promising to deepen our understanding of groundwater levels and their intricate behaviours.

The project will be organized into seven tasks, utilizing a multidisciplinary approach to address the study area comprehensively. The first two tasks (Task 1 & 2) will be carried out concurrently. They will construct the necessary seismic and geophysical datasets and establish the geotectonic and geohydrological framework for a specific target area (case study) and for the broader study region. These initial steps will provide a foundational understanding essential for subsequent analyses.

Task 3 will concentrate on spatially characterizing the structure of the groundwater system in South Portugal using ambient noise techniques such as ambient noise tomography and ambient noise autocorrelations/interferometry. Previous seismic tomography studies have extensively covered the crust and upper mantle beneath Portugal [P1, and references therein]. On a more localized scale, [P3] developed a regional ambient noise tomographic model, incorporating seafloor- and land-based data, with a specific focus on the Southwest Portuguese margin. However, these investigations primarily addressed geodynamics and tectonics, lacking emphasis on hydrogeological aspects. Our study aims to delineate the complex 3D geological features influencing aquifer properties. Seismic ambient noise has emerged as an effective tool for examining hydrological basin geometry [e.g., P3, P4], enabling the creation of a detailed and accurate shallow subsurface structure model. We will integrate results from local earthquake tomography [P5] and existing active seismic experiments to generate a more detailed image. This approach will deepen our understanding of the geological properties of groundwater systems, thereby contributing to informed groundwater resource management and the activities conducted in Taks 4-6.

Task 4 will focus on comprehensively understanding temporal variations in groundwater flow using seismic interferometry within a selected aquifer. To assess the effectiveness of the proposed monitoring system, we have chosen a well-known and extensively documented aquifer in the Algarve, leveraging our profound understanding of its geological and hydrogeological characteristics. We will densely sample the aquifer region to extract maximum insights from the results obtained through seismic interferometry. This will involve deploying a temporary short-period seismic network, conducting geoelectric soundings, utilizing InSAR and GPS observations, and integrating piezometric data. By adopting this multidisciplinary approach, we aim to master the interpretation of seismic results and gain a holistic understanding of groundwater dynamics in the aquifer.

Task 5 concerns a detailed analysis of the spatio-temporal evolution of the seismicity and its relationship with the groundwater dynamics in the aquifers. In Task 6, we will expand the application of ambient noise seismic interferometry, as implemented in Task 4, to encompass more than 30 permanent seismic stations covering the entire Southern Portuguese region. This approach will assist in developing effective monitoring strategies for sustainable groundwater management. By analyzing a minimum of 15 years of data dating back to 2008/2009, we aim to deepen our understanding of groundwater-related hazards. Changes in seismic wave velocities can serve as indicators of potential hazards such as subsidence, land instability, or the impact of hydrological changes on infrastructure. Monitoring these variations is crucial for assessing and mitigating associated risks. Despite the increasing popularity of seismic arrays as a cost-effective approach to aquifer monitoring [e.g. 3, 4], their exploration in Portugal still needs to be implemented. The geological features influencing aquifer properties often exhibit complex geometries with dimensions spanning several orders of magnitude. Consequently, the project team will require diverse survey layouts. Similar to Task 4, we will rely on available piezometric, resistivity, InSAR, and GPS data.

In Task 7, we will consolidate the knowledge acquired from the preceding activities into a final comprehensive geodynamic model of Southern Portugal and the dynamics of its groundwater systems. This structured approach ensures a thorough exploration, ranging from its geotectonic framework to temporal variations, culminating in developing practical monitoring strategies and transferable knowledge for broader water management applications. Depending on data availability, we will extend our insights to other regions grappling with water management challenges.

The project's results will be disseminated through leading international peer-reviewed journals, as well as national and international conferences and workshops. Active involvement of junior researchers and students will ensure broad dissemination of results. Additionally, project outcomes will be shared with the educational community through initiatives such as Seismology-at-Schools. Throughout the project, ongoing communication with stakeholders such as IPMA, Agência Portuguesa do Ambiente (APA), and municipal authorities will be maintained to ensure the relevance and applicability of the research findings.

Along this text, and in the all the following ones, all references are identified as [number], while the team publications from the team are referred as [Pnumber].