Executive summary: This document describes the structure and contents of the public website set up for PACIFIC on 29th November 2018 with the URL http://www.pacific-h2020.eu and updated in August 2020 to give more visibility to the expected impact of the project on mineral exploration in Europe, and reflect changes in the consortium. The website is based on Responsive web design (RWD), which provides an optimal viewing and interaction experience — easy reading and navigation with a minimum of resizing, panning, and scrolling — across a wide range of devices (from desktop computer monitors to mobile phones).

On the PACIFIC public website, you can find information about the project objectives and results, the concept, work plan and expected impact, together with the list of participants, external advisors and projects identified for clustering opportunities. The website also acknowledges the financial support received under the European Union’s Horizon 2020 research and innovation programme with the EU emblem as well as a specific statement. This is visible at the bottom of every webpage.

Throughout the project the PACIFIC public website will become a major tool to present the project research outcomes to a wide audience with: links to scientific peer-reviewed publications, project documentation, public deliverables and press releases available for download. On-going activities will also be regularly updated and communicated through news and events.

Download the PACIFIC flyer https://www.pacific-h2020.eu/wp-content/uploads/pacific-flyer.pdf 

Noise-based ballistic wave passive seismic monitoring. Part 1: body waves

Unveiling the mechanisms of earthquake and volcanic eruption preparation requires improving our ability to monitor the rock mass response to transient stress perturbations at depth. The standard passive monitoring seismic interferometry technique based on coda waves is robust but recovering accurate and properly localized P- and S-wave velocity temporal anomalies at depth is intrinsically limited by the complexity of scattered, diffracted waves. In order to mitigate this limitation, we propose a complementary, novel, passive seismic monitoring approach based on detecting weak temporal changes of velocities of ballistic waves recovered from seismic noise correlations. This new technique requires dense arrays of seismic sensors in order to circumvent the bias linked to the intrinsic high sensitivity of ballistic waves recovered from noise correlations to changes in the noise source properties. In this work we use a dense network of 417 seismometers in the Groningen area of the Netherlands, one of Europe's largest gas fields. Over the course of 1 month our results show a 1.5 per cent apparent velocity increase of the P wave refracted at the basement of the 700-m-thick sedimentary cover. We interpret this unexpected high value of velocity increase for the refracted wave as being induced by a loading effect associated with rainfall activity and possibly canal drainage at surface. We also observe a 0.25 per cent velocity decrease for the direct P-wave travelling in the near-surface sediments and conclude that it might be partially biased by changes in time in the noise source properties even though it appears to be consistent with complementary results based on ballistic surface waves presented in a companion paper and interpreted as a pore pressure diffusion effect following a strong rainfall episode. The perspective of applying this new technique to detect continuous localized variations of seismic velocity perturbations at a few kilometres depth paves the way for improved in situ earthquake, volcano and producing reservoir monitoring.

Executive Summary: The passive seismic survey of the La Cruces mine site was initiated during discussion between partners of the PACIFIC and INFACT H2020 projects in December 2018. The initial design for the deployment covered a large area, about 7 x 4 km extending to the north and south of the mine but this was reduced to a smaller tighter 2 x 1 km array in February 2019. A collapse of the northside of the open pit then eliminated the possibility of placing nodes to the west of the pit and this resulted in an even smaller array. Data treatment proved to be very difficult for several reasons. The array was smaller than originally planned, but more importantly a significant proportion of the nodes, about 30%, were placed in the pit. The large differences in elevation between adjacent nodes and the differences in orientation of pit walls and terraces introduced unanticipated difficulties in processing the seismic data. 

We used 33 days of passive seismic records to retrieve the fundamental mode of Rayleigh waves propagating in the subsurface. We mostly used man-made ambient noise generated in the vicinity of the mine in the period band [0.3 - 1.5] s. Strong anthropogenic noise in the middle of the array forced us to use one-bit normalization and very intense pre-processing to retrieve usable cross-correlation signals. We were able to pick individual group and phase velocity dispersion curves from correlations computed between the majority of sensor pairs for stations separated by less than 2 km. We retained about 15% of all possible dispersion curves after a thorough quality check based on expert visual inspection. The aperture of the array and the frequency content of the noise allowed us to invert a velocity model down to 500 m depth. Long offsets are mainly discarded inducing a poor coverage of the central part of the pit. A high velocity anomaly beneath the northern part of the site where topography is not a problem and where the array is denser can be resolved and could correspond to the massive sulphide ore body at depth. The depth of cover in the north-eastern part of the study area is well represented by the iso-velocity surface of 750 m/s.

Virtual Sources of Body Waves from Noise Correlations in a Mineral Exploration Context.

The extraction of body waves from passive seismic recordings has great potential for monitoring and imaging applications. The low environmental impact, low cost, and high accessibility of passive techniques makes them especially attractive as replacement or complementary techniques to active‐source exploration. There still, however, remain many challenges with body‐wave extraction, mainly the strong dependence on local seismic sources necessary to create high‐frequency body‐wave energy. Here, we present the Marathon dataset collected in September 2018, which consists of 30 days of continuous recordings from a dense surface array of 1020 single vertical‐component geophones deployed over a mineral exploration block. First, we use a cross‐correlation beamforming technique to evaluate the wavefield each minute and discover that the local highway and railroad traffic are the primary sources of high‐frequency body‐wave energy. Next, we demonstrate how selective stacking of cross‐correlation functions during periods where vehicles and trains are passing near the array reveals strong body‐wave arrivals. Based on source station geometry and the estimated geologic structure, we interpret these arrivals as virtual refractions due to their high velocity and linear moveout. Finally, we demonstrate how the apparent velocity of these arrivals along the array contains information about the local geologic structure, mainly the major dipping layer. Although vehicle sources illuminating array in a narrow azimuth may not seem ideal for passive reflection imaging, we expect this case will be commonly encountered and should serve as a good dataset for the development of new techniques in this domain.

Executive summary: To create synergies and optimise project results and impact, the PACIFIC project dedicates the Work Package 7 to collaboration and clustering with other research projects under the same call topic, and other relevant projects in the field funded by Horizon 2020 (H2020). PACIFIC partners thus collaborate with ongoing research initiatives in the mineral exploration area.

During the first year of the project, the collaboration took several forms, that are developed in this deliverable according to the following axes:

1. Joint activities organised with other projects in the cluster;
2. Participation in international events and conferences with other H2020 related projects;
3. Ongoing and future collaborations.

This report must be understood as the first of three reports on joint events with other research projects, that will be produced through the duration of the project: D7.2 (M12), D7.3 (M24) and D7.4 (M36). Thus, the information provided, especially in the “Ongoing and future collaborations” section, will be reviewed or updated in next reports. 

Executive summary: Across the globe, the mineral industry is seeking new technologies to replace or complement existing geological, geochemical and geophysical methods to improve exploration efficiency at depth and to help design safer and more productive mines. These industries are increasingly using seismic methods for a wide range of commodities including base metals, uranium, diamonds, and precious metals. Seismic methods usually can be used for direct targeting of mineral deposits but particular care must be taken during acquisition and processing of the data. To achieve the best results, different processing sequences based on the target of the project are applied. Here we compare and discuss how such workflows are used when treating active seismic data in order to provide a basis for their use in the development of the passive seismic methods that form the basis of the PACIFIC project.

Technique now possible due to improvements in lithium batteries which power monitoring equipment

Article in the Canadian press by Jeff Walters · CBC News · Posted: Jun 12, 2019 1:28 PM ET  https://www.cbc.ca/news/canada/thunder-bay/thunder-bay-pacific-new-exploration-1.5172168