Executive Summary: Seismic methods provide high-resolution images of geologic structures hosting mineral deposits and, in a few cases, can be used for direct targeting of deposits. Active reflection techniques have been successfully used in the minerals sphere, especially for structural control on deep targets. Although useful, a disadvantage of this methodology is that it is expensive and logistically difficult in locations without easy access for source generation. In contrast to active seismology, passive methods exploit ambient seismic noise and do not require specific seismic sources. In this report, we compare active and passive seismic methods in general and discuss different data processing sequences that have been used in previous passive seismic studies. The quality of the results in passive seismic methods strongly depends on (1) the spatial-temporal properties of the noise source distribution and (2) the number and disposition of seismic receiver pairs on which the noise correlation is performed. We then discuss how to apply these processing sequences to extract body-waves in the PACIFIC project, with a view to developing reflection seismic images analogous to active reflection seismic work.

Executive summary: The Winter School on Sustainable Mineral Exploration was jointly organized by two European projects—PACIFIC and INFACT. The event was held at the International Campus of Andalusia in Huelva, Spain, between the 9th and 12th March 2020. The Winter School was divided in 3 lecture sessions, 1 practical session, and 2 visits to mining sites. The main goal of this school was to present the techniques and knowledge on sustainable mineral exploration that have been developed within the INFACT and PACIFIC projects. The school targeted an audience of European master students, PhDs and post-doctoral researchers. A total of 40 students, including 15 from the University of Huelva, physically attended the school. An additional 13 students participated in parts of the school via video conference, since unfortunately due to travel restrictions stemming from the COVID-19 pandemic those 13 students were unable to attend in person. Videoconferencing was a last-minute adaptation made by the Winter School to allow for the participation of individuals under travel bans, quarantine, or other restrictions. Students (both physical and remote attendees) came from 13 countries. The results of the anonymous survey conducted at the end of the school reveal that the event was a success, despite the ongoing COVID-19 crisis.

Retrieving reflection arrivals from passive seismic data using Radon correlation

Since explosive and impulsive seismic sources such as dynamite, air guns, gas guns or even vibroseis can have a big impact on the environment, some companies have decided to record ambient seismic noise and use it to estimate the physical properties of the subsurface. Big challenges arise when the aim is extracting body waves from recorded passive signals, especially in the presence of strong surface waves. In passive seismic signals, such body waves are usually weak in comparison to surface waves that are much more prominent. To understand the characteristics of passive signals and the effect of natural source locations, three simple synthetic models were created. To extract body waves from simulated passive signals we propose and test a Radon-correlation method. This is a time-spatial correlation of amplitudes with a train of time-shifted Dirac delta functions through different hyperbolic paths. It is tested on a two-layer horizontal model, a three-layer model that includes a dipping layer (with and without lateral heterogeneity) and also on synthetic Marmousi model data sets. Synthetic tests show that the introduced method is able to reconstruct reflection events at the correct time-offset positions that are hidden in results obtained by the general cross-correlation method. Also, a depth migrated section shows a good match between imaged horizons and the true model. It is possible to generate off-end virtual gathers by applying the method to a linear array of receivers and to construct a velocity model by semblance velocity analysis of individually extracted gathers.

Monitoring of fields using body and surface waves reconstructed from passive seismic ambient noise

There are important economic, environmental and societal reasons for monitoring production from oil, gas and geothermal fields. Unfortunately, standard microseismic monitoring is often not useful due to low levels of microseismicity. We propose to use body and surface waves reconstructed from ambient seismic noise for such monitoring. In this work, we use seismic data recorded from a dense sensor array at the Groningen gas field in northern Holland and show how direct P-waves can be extracted from the ambient noise cross correlations and then used to monitor seismic velocity variations over time. This approach has advantages over the use of coda wave interferometry due to the ability to localise such changes in the subsurface. We show how both direct and refracted (head) P-waves as well as Rayleigh surface waves can be used for such field monitoring, with changes of ∼1% being resolved. Both fundamental and first overtone Rayleigh waves are used to localise such changes, which correspond nicely to known geology to within 100 m.

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.