Geodetic Campaigns Research Articles

Geomorphological evidence for volcano-tectonic deformation along the unstable western flank of Cumbre Vieja Volcano (La Palma)

In 2021, La Palma's southern volcanic complex Cumbre Vieja erupted for its longest period in historic times. Although the geological record shows no evidence for a collapse of Cumbre Vieja, ground deformation studies and field observations suggest that its western flank is moving seawards, following the direction of previous collapses of the island. To better estimate the hazard of a potential flank collapse of Cumbre Vieja, it is important to identify the lateral extent and depth of the mobile sector. Here, we analyse the volcano-tectonic deformation along Cumbre Vieja's western flank, based on geomorphological analysis of combined topographic and new ship-born bathymetric data as well as the analysis of shallow seismicity records associated with the 2021 eruption. In our interpretation, the shoreline-crossing Puerto Naos Ridge results from tectonic uplift accompanying transpressional deformation along the northern boundary of Cumbre Vieja's moving flank, therefore decoupling a stable sector in the north from the mobile sector farther south. The proposed moving sector is consistent in scale with previous ground deformation studies and documented flank collapses of structurally similar volcanoes. We present a workflow for semi-automatically detecting boundaries of unstable volcanic flanks based on morphological changes captured in digital elevation data. The method correctly delineated the known boundaries of the unstable flanks of Mt. Etna and Kilauea volcanoes. The ability to constrain potential boundaries of unstable volcanic flanks should inform the planning of future geophysical and geodetic campaigns aiming to identify precursory signals of potential flank failures.

Exploiting satellite SAR for archaeological prospection and heritage site protection

ABSTRACT Optical and Synthetic Aperture Radar (SAR) remote sensing has a long history of use and reached a good level of maturity in archaeological and cultural heritage applications, yet further advances are viable through the exploitation of novel sensor data and imaging modes, big data and high-performance computing, advanced and automated analysis methods. This paper showcases the main research avenues in this field, with a focus on archaeological prospection and heritage site protection. Six demonstration use-cases with a wealth of heritage asset types (e.g. excavated and still buried archaeological features, standing monuments, natural reserves, burial mounds, paleo-channels) and respective scientific research objectives are presented: the Ostia-Portus area and the wider Province of Rome (Italy), the city of Wuhan and the Jiuzhaigou National Park (China), and the Siberian “Valley of the Kings” (Russia). Input data encompass both archive and newly tasked medium to very high-resolution imagery acquired over the last decade from satellite (e.g. Copernicus Sentinels and ESA Third Party Missions) and aerial (e.g. Unmanned Aerial Vehicles, UAV) platforms, as well as field-based evidence and ground truth, auxiliary topographic data, Digital Elevation Models (DEM), and monitoring data from geodetic campaigns and networks. The novel results achieved for the use-cases contribute to the discussion on the advantages and limitations of optical and SAR-based archaeological and heritage applications aimed to detect buried and sub-surface archaeological assets across rural and semi-vegetated landscapes, identify threats to cultural heritage assets due to ground instability and urban development in large metropolises, and monitor post-disaster impacts in natural reserves.

Searching for possible precursors of mining-induced ground collapse using long-term geodetic monitoring data

The problem of the ground collapses is common for the regions affected by the underground mining, as well as for the areas prone to the sinkholes of natural or human genesis. This paper describes the case of the ground surface collapse occurred in 2013 above the active Saranovsky chromite ore underground mine that has been operating for over eighty years. The results of pre- and post-failure high-precision levelling of the ground surface are presented. The monitoring network includes more than one hundred surveying points covering the area of about 1 km2 and since 2006 geodetic measurements have been conducted on an annual basis. The analysis pointed to a complex deformation process, manifested in the cyclic succession of subsidence and uplift of the surface. A local zone of continuous surface subsidence was identified immediately above the site of the future collapse. The deformations started several years before the failure. The extent of the subsiding area increased gradually, approximately approaching the size of the collapse (over 7000 m2). During the three-year period preceding the collapse, this area expanded by over a factor of ten, and the cumulated subsidence rate doubled. However, since the monitoring points located within the sinkhole area were lost, the data of the geodetic campaign carried out before the collapse were insufficient to estimate the value of the subsidence preceding the failure. Our results demonstrate, that in hard rocks mining-induced deformations can develop in utterly localized way. The progression of the subsidence was detected generally within the area of the future failure and did not extend significantly beyond its contours. In this paper, we highlight the importance of further development of the monitoring techniques and justification of hazardous deformation criteria for the early warning systems in mining regions and sinkhole-prone areas.

A transportable quantum gravimeter employing delta-kick collimated Bose\u2013Einstein condensates

Gravimetry with low uncertainty and long-term stability opens up new fields of research in geodesy, especially in hydrology and volcanology. The main limitations in the accuracy of current generation cold atom gravimeters stem from the expansion rate and the residual centre-of-mass motion of their atomic test masses. Our transportable quantum gravimeter QG-1 aims at overcoming these limitations by performing atom interferometry with delta-kick collimated Bose–Einstein condensates generated by an atom chip. With our approach we anticipate to measure the local gravitational acceleration at geodetic campaigns with an uncertainty less than 1 nm/s2 surpassing the state-of-the-art classic and quantum based systems. In this paper, we discuss the design and performance assessment of QG-1.Graphical abstract

A VLBI experiment using a remote atomic clock via a coherent fibre link

We describe a VLBI experiment in which, for the first time, the clock reference is delivered from a National Metrology Institute to a radio telescope using a coherent fibre link 550 km long. The experiment consisted of a 24-hours long geodetic campaign, performed by a network of European telescopes; in one of those (Medicina, Italy) the local clock was alternated with a signal generated from an optical comb slaved to a fibre-disseminated optical signal. The quality of the results obtained with this facility and with the local clock is similar: interferometric fringes were detected throughout the whole 24-hours period and it was possible to obtain a solution whose residuals are comparable to those obtained with the local clock. These results encourage further investigation of the ultimate VLBI performances achievable using fibre dissemination at the highest precision of state-of-the-art atomic clocks.

Historical and recent sea level rise and land subsidence in Marina di Ravenna, northern Italy

The regions facing the northern Adriatic Sea are particularly vulnerable to sea-level rise. Several trade ports are located there, and the area is important from social and economical viewpoints. Since tourism and cultural heritage are a significant source of income, an increase in sea-level could hinder the development of these regions. One of the longest sea-level time series in the northern Adriatic, which goes back to the late 1880s, has been recorded at Marina di Ravenna, in Emilia-Romagna region. The record is anomalous, showing a rate of increase that largely exceeds that observed in nearby stations. During the last few decades, geodetic campaigns based on geometric high precision leveling, SAR interferometry, and GPS have monitored the Ravenna area. In this work, tide gauge observations are merged with yet unpublished geodetic data, aiming at a coherent interpretation of vertical land movements. We confirm that land subsidence is the major cause of relative sea-level change at Marina di Ravenna, at least during the period allowing for a quantitative analysis (1990-2011). The rate of absolute sea-level change (2.2±1.3 mm yr−1 during the same time period), given by the difference between the rate of relative sea-level change and the rate of subsidence, is consistent with the rate of absolute sea-level change observed by altimetry in the northern Adriatic Sea.

Spatial distribution and change in the surface ice‐velocity field of vestfonna ice cap, nordaustlandet, svalbard, 1995–2010 using geodetic and satellite interferometry data

Pohjola, V.A., Christoffersen, P., Kolondra, L., Moore, J.C., Pettersson, R.S., Schäfer, M., Strozzi, T. and Reijmer, C.H., 2011. Spatial distribution and change in the surface ice‐velocity field of Vestfonna ice cap, Nordaustlandet, Svalbard, 1995–2010 using geodetic and satellite interferometry data. Geografiska Annaler: Series A, Physical Geography. 93, 323–335. DOI: 10.1111/j.1468‐0459.2011.00441.xDuring 2007 we launched a geodetic campaign on the Svalbard ice cap Vestfonna in order to estimate the velocity field of the ice cap. This was done within the frame of the IPY project KINNVIKA. We present here the velocity measurements derived from our campaigns 2007–2010 and compare the geodetic measurements against InSAR velocity fields from satellite platforms from 1995/96 and 2008. We find the spatial distribution of ice speeds from the InSAR is in good agreement within the uncertainty limits with our geodetic measurements. We observe no clear indication of seasonal ice speed differences, but we find a speed‐up of the outlet glacier Franklinbreen between the InSAR campaigns, and speculate the outlet is having a surge phase.

Height Determination of Qomolangma Feng (MT. Everest) in 2005

Since the 1960s China has carried out several geodetic campaigns for measuring the height of Qomolangma Feng-Mt. Everest independently or in cooperation with foreign countries. Large scale geodetic field work and data processing have been done in the campaigns, dealing with positioning, height determination, gravimetry, astronomical measurement and atmospheric reflection observation etc. Some survey tasks were done in order to improve the accuracy and reliability for the height determination of Mt. Everest. These tasks include setting up of a survey target on the summit of Mt. Everest (MES) in the 1975, 1992 and 2005 campaigns, joint use of GPS, laser ranging and trigonometric levelling in the 1992 and 2005 campaigns, exploration of the thickness of the ice-snow layer on the summit and refinement of the local gravity field including the geoid in the northern slope area with new surface ground gravity data, DTM and astro-gravity levelling or GPS levelling results in the campaigns mentioned. It is the first time in China that the thickness of the ice-snow layer on the summit was measured by ground penetrating radar integrated with GPS in the 2005 campaign. The orthometric heights of the snow surface and rock surface of the summit were determined as 8847.93m and 8844.43m respectively in the 2005 campaign. The rate of decrease of the snow summit of Mt. Everest between 1992 and 2005 was 1.8cm/a.

The results of the third geodetic campaign in the local geodynamic test area of the MAO NAS of Ukraine

The high-precision coordinates of reference (reduction) points of stations located in the geodynamic area of the MAO NAS of Ukraine were determined in the local topocentric coordinate system. The local geodetic ties (eccentricities) between the reference points of the GPS station “Kiev/Goloseev” and satellite laser location station “Goloseev-Kiev” that are equal to 100.2358 m, −11.0398 m, −85.8256 m on the X, Y, Z axes, respectively, were obtained in the ITRF97 system as of the epoch 1997.0. The coordinates of the reference point of the station “Goloseev-Kiev” were determined in the ITRF97 system as of the epoch 1997.0 by adding local geodetic ties to the coordinates of the reference point of the GPS station “Kiev/Goloseev.” They were compared with the estimates of the coordinates of these stations obtained by the methods of cosmic geodesy and geodynamics. The local deformations of the geodynamic area that took place in the 1997–2006 period were estimated and the conclusion was made about the existence of certain trends with respect to the local displacements of the points of the geodynamic area of the MAO NAS of Ukraine.

Progress in technology for the 2005 height determination of Qomolangma Feng (Mt. Everest)

In 2005 China carried out a new geodetic campaign for the height determination of Qomolangma Feng——Mt. Everest (QF in short). The technical progresses in geodesy for the 2005 campaign are presented in the paper. GPS positioning was the key technique in the campaign. After summarizing the experiences and lessons of the GPS positioning on the QF summit in the previous QF height determination campaigns, some measures were taken to raise the accuracy and reliability of the height determination with GPS techniques. In order to raise the accuracy of the height determination of the QF summit with classical geodetic techniques, laser ranging was used together with the trigo-nometric levelling in the 2005 campaign. It is the first time in China the thickness of the ice-snow layer on the QF summit was measured by ground penetrating radar integrated with GPS. The local gravity field and geoid in the QF area was improved on the basis of earth gravity field model integrated with new ground gravity data, DTM data and GPS leveling data in the QF area. In the 2005 campaign the normal height and orthometric height (height above sea level) of the snow surface of the QF summit were obtained as 8846.67 m and 8847.93 m respectively. The orthometric height of the rock surface of the QF summit is 8844.43 m，and the thickness of the ice-snow layer on the QF summit is 3.50 m.

On crustal movement in Mt. Qomolangma area

Mt. Qomolangma lies in the collision zone between the fringe of Eurasia plate and Indian plate. The crustal movement there is still very active so far. In the past three decades China carried out five geodetic campaigns in Mt. Qomolangma and its north vicinal area, independently or cooperatively with other countries, including triangulation, leveling, GPS positioning, atmospheric, astronomical and gravity measurements. On the basis of the observation results achieved in the campaigns the crustal movements in the area were studied and explored. A non-stationary phenomenon both in time and space of the crustal vertical movement in the area is found. There seems to be some relevance between the phenomenon of non-stationary in time and seismic episode in China. The phenomenon of non-stationary in space is possibly relevant to the no-homo- geneity of crustal medium and non-uniform absorption of terrestrial stress. The horizontal crustal movement in the area is in the direction of NEE at a speed of 6—7 cm per year, and the trend of strike slip movement is manifested evidently in the collision fringe of Indian plate and Qinghai-Xizang block.

Deformation actuelle de la chaine de Belledonne (massifs cristallins externes alpins, France); comparaison triangulation historique-GPS

Deformation actuelle de la chaine de Belledonne (massifs cristallins externes alpins, France); comparaison triangulation historique-GPS

Astrophysical Results from Geodetic VLBI Campaigns

Geodetic VLBI observations of extragalactic radio sources –designed to measure earth orientation parameters– are performed regularly since more than 10 years now. In different campaigns about 20 Quasars and BL Lacs are being monitored at 2.3 and 8.4 GHz. The high duty-cycle of these observations (every month for IRIS-S) and the resulting enormous data base allow to study the milliarcsecond structures and their variations simultaneously at two frequencies on short timescales. Since the accuracy of baseline determination and measurement of earth rotation parameters has reached a limit where source structure contributions become significant, there is substantial interest to monitor and correct for the source structure “effects”. Therefore we perform a regular analysis of sources selected from IRIS-S (high north-south resolution and almost circular beam for low declination sources) and EUROPE (high sensitivity due to large telescopes) campaigns covering a maximum time base of 10 years (1983–1993). The (undesired) structure of the sources leads to an occasional updating of the source catalogue in order to have “pointlike” sources which are observed 10–15 times for three to seven minutes during 24 hours. Meanwhile about 50 sources have been observed in geodetic campaigns. The comparatively poor data quality requires careful calibration with a source whose structure is well–known from high dynamic range observations (e.g. the blazar 1803+784). The dynamic range of these maps is limited to 1:50. The merit of this database lies obviously in the monthly persecution of structural changes in extragalactic radio sources over at best 10 years time and the filling of the gaps between high dynamic range observations. Sources which are presently of particular interest to us, include 1803+784, 4C39.25, 0528+134, 3C454.3 and OJ287.