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EMSO is a distributed Research Infrastructure currently comprising nine Regional Facilities (RFs) and three shallow water test sites, strategically located all the way from the southern entrance of the Arctic Ocean across to the North Atlantic through the Mediterranean to the Black Sea. Since the beginning of 2021 Norway has been integrated as a new EMSO ERIC member, extending the geographical coverage to the Nordic Sea and the Arctic. EMSO’s extension will benefit from an experienced team managing moored observatories, ocean gliders and the Mohn Ridge Seafloor and Water Column Observatory.

Special issue 9th MARTECH: International Workshop on Marine Technology: 16-18 June 2021, Vigo, Spain.-- 2 pages, 1 figure, The European Multidisciplinary Seafoor and water Column Observatory (EMSO, www.emso.eu) is a distributed research infrastructure (RI), composed of fxed-point deep-sea observatories and shallow water test sites at strategic environmental locations from the southern entrance of the Arctic Ocean all the way through the North Atlantic through the Mediterranean to the Black Sea. Working as a single powerful system, it is a valuable new tool for researchers and engineers looking for long time series of high-quality and high-resolution data to study and continuously monitor complex processes interactions among the geosphere, biosphere, hydrosphere and atmosphere, as well as to test, validate and demonstrate new marine technologies

This document presents a strategy for ENVRI community communication and engagement actions. Such activities aim to further build the community of environmental research infrastructures (RI), with a special eye on the engagement of the RI scientific communities. The idea is to promote the RI collaboration benefits and inform about the opportunities offered thanks to the integrative and harmonization work among the RIs. However, the main goal of this strategy is to increase the visibility and two-way communications and engagement of the external stakeholders for the benefit of the ENVRI community as much as the collaborating RIs. This deliverable presents a summary of communications activities that are more possible, effective, or economical to do together rather than by individual member research infrastructures. We hope that such activities will increase the understanding of the Earth system's complexity and the necessity of studying the system holistically and the understanding of each specific RI's role in that system. Since such understanding is very much dependent on the in-situ observations, i.e., on the environmental RIs, the goal of the communications activities is to put the data and services provided by the RIs into the spotlight, and in that way attract more users, and eventually deliver a top-level multidisciplinary science.

Since the first underground nuclear explosion, carried out in 1958, the analysis of seismic signals generated by these sources has allowed seismologists to refine the travel times of seismic waves through the Earth and to verify the accuracy of the location algorithms (the ground truth for these sources was often known). Long international negotiates have been devoted to limit the proliferation and testing of nuclear weapons. In particular the Treaty for the comprehensive nuclear test ban (CTBT), was opened to signatures in 1996, though, even if it has been signed by 178 States, has not yet entered into force, The Treaty underlines the fundamental role of the seismological observations to verify its compliance, by detecting and locating seismic events, and identifying the nature of their sources. A precise definition of the hypocentral parameters represents the first step to discriminate whether a given seismic event is natural or not. In case that a specific event is retained suspicious by the majority of the State Parties, the Treaty contains provisions for conducting an on-site inspection (OSI) in the area surrounding the epicenter of the event, located through the International Monitoring System (IMS) of the CTBT Organization. An OSI is supposed to include the use of passive seismic techniques in the area of the suspected clandestine underground nuclear test. In fact, high quality seismological systems are thought to be capable to detect and locate very weak aftershocks triggered by underground nuclear explosions in the first days or weeks following the test. This PhD thesis deals with the development of two different seismic location techniques: the first one, known as the double difference joint hypocenter determination (DDJHD) technique, is aimed at locating closely spaced events at a global scale. The locations obtained by this method are characterized by a high relative accuracy, although the absolute location of the whole cluster remains uncertain. We eliminate this problem introducing a priori information: the known location of a selected event. The second technique concerns the reliable estimates of back azimuth and apparent velocity of seismic waves from local events of very low magnitude recorded by a trypartite array at a very local scale. For the two above-mentioned techniques, we have used the crosscorrelation technique among digital waveforms in order to minimize the errors linked with incorrect phase picking. The cross-correlation method relies on the similarity between waveforms of a pair of events at the same station, at the global scale, and on the similarity between waveforms of the same event at two different sensors of the try-partite array, at the local scale. After preliminary tests on the reliability of our location techniques based on simulations, we have applied both methodologies to real seismic events. The DDJHD technique has been applied to a seismic sequence occurred in the Turkey-Iran border region, using the data recorded by the IMS. At the beginning, the algorithm was applied to the differences among the original arrival times of the P phases, so the cross-correlation was not used. We have obtained that the relevant geometrical spreading, noticeable in the standard locations (namely the locations produced by the analysts of the International Data Center (IDC) of the CTBT Organization, assumed as our reference), has been considerably reduced by the application of our technique. This is what we expected, since the methodology has been applied to a sequence of events for which we can suppose a real closeness among the hypocenters, belonging to the same seismic structure. Our results point out the main advantage of this methodology: the systematic errors affecting the arrival times have been removed or at least reduced. The introduction of the cross-correlation has not brought evident improvements to our results: the two sets of locations (without and with the application of the cross-correlation technique) are very similar to each other. This can be commented saying that the use of the crosscorrelation has not substantially improved the precision of the manual pickings. Probably the pickings reported by the IDC are good enough to make the random picking error less important than the systematic error on travel times. As a further justification for the scarce quality of the results given by the cross-correlation, it should be remarked that the events included in our data set don’t have generally a good signal to noise ratio (SNR): the selected sequence is composed of weak events ( magnitude 4 or smaller) and the signals are strongly attenuated because of the large distance between the stations and the hypocentral area. In the local scale, in addition to the cross-correlation, we have performed a signal interpolation in order to improve the time resolution. The algorithm so developed has been applied to the data collected during an experiment carried out in Israel between 1998 and 1999. The results pointed out the following relevant conclusions: a) it is necessary to correlate waveform segments corresponding to the same seismic phases; b) it is not essential to select the exact first arrivals; and c) relevant information can be also obtained from the maximum amplitude wavelet of the waveforms (particularly in bad SNR conditions). Another remarkable point of our procedure is that its application doesn’t demand a long time to process the data, and therefore the user can immediately check the results. During a field survey, such feature will make possible a quasi real-time check allowing the immediate optimization of the array geometry, if so suggested by the results at an early stage.