Lithospheric structure across the Himalayan-Tibetan orogen: a petrological and geophysical study

Abstract HKT-ISTP 2013 A

Sea level variability and trends in the Adriatic Sea \uedn 1993-2008 from tide gauges and satellite altimetry. Physics and Chemistry of the Earth

The scope of this paper is to give a consistent view of the low frequency sea level variability in the Adriatic Sea from both satellite altimetry and tide gauge records. We analyze 16 years of sea level observations from multi-satellite altimetry and tide gauge records in the time interval 1993\u20132008. First, the impact of the corrections applied to the altimetry-derived sea level variations and the consistency of the altimetric and the tide gauge sea level observations are evaluated. Both observations are then used to characterize sea level trends, interannual variability and land vertical motion in the Adriatic region. Eight tide gauges along the coast show very coherent interannual sea level variations, with an increase in sea level before 2001 and decrease afterwards. The average of the eight de-seasoned time-series agrees with the basin average of the altimeter data, with correlation coefficient 0.84 and root mean square difference 12 mm. The linear change is higher for altimetry than for tide gauges and strongly depends on the length of the time-interval, being 3.2 \ub1 0.3 mm/yr and 1.9 \ub1 0.3 mm/yr in the interval 1993\u20132008. The steric contribution to sea level change correlates well with the sea level suggesting that the low frequency variability is likely related to oceanic and climatic processes and mainly due to temperature and salinity variations. The decadal sea level variability is correlated in Adriatic and Eastern Mediterranean, anti-correlated in Adriatic and Ionian Sea. At a given location, the trend of the differences of sea level observations by tide gauges and co-located satellite altimetry gives the vertical land motion, if we assume that the sea level signals are truly common. We find trends statistically significant at the 90% confidence level at two locations, that indicate land uplift along the eastern coast in Rovinj (3.0 \ub1 1.2 mm/yr) and land subsidence in Marina di Ravenna (1.5 \ub1 1.1 mm/yr), while at other locations, e.g. in Trieste (1.3 \ub1 1.1 mm/yr) the significance is lower. The results agree in general in sign with GPS derived rates, but not in magnitude, like in Marina di Ravenna, where the strong subsidence measured by GPS is related to the local anthropogenic subsidence. The differences are partly explained by the spatial distance between the tide gauge and the co-located altimeter locations

Vertical crustal movements in Italy from tidal gauge and satellite altimetry data

Geophysical Research Abstracts Vol. 12, EGU2010-12894-3,2010 EGU General Assembly 2010 Vienna, 2-7 /05/201

Vertical land movement for the Italian coasts by altimetric and tide gauges measurements

The difference between the surface height observed by satellite altimetry and tide gauges gives an estimation of vertical land movements. We use this approach for determining vertical crustal movements along Italian coasts. The major problem with the altimetry is to acquire data near to the coastlines. We explore satellite data statistically to understand in which tide gauge stations the methodology of comparison with the satellite observations can be applied. We analyze the two different datasets (tide gauges and satellite altimetry) in order to determine under which circumstances it is possibile to calculate the tectonic rates from the sea level trends differences. We try to approach the coast as much as possible and we determine the apparent tectonic rates in 12 selected stations along Italian coastlines. We found subsidence in Puglia coasts and in Lampedusa station, uplift in Liguria Sea littoral and stability along the central coasts of Italy, like in Cicitavecchia and in Ancona. The results are complementary to vertical land movements achievable with GPS

Time Evolution of Deformation Using Time Series of Differential Interferograms: Application to La Palma Island (Canary Islands)

Differential interferometry is a very powerful tool for detecting changes in the Earth's crust where coherence conditions are good, but is difficult to employ in some volcanic areas due to dense vegetation. We apply two differential InSAR methods using the time series associated with the interferograms to perform a phase analysis on a data set for La Palma island (Canary Islands) from the ERS-1 and ERS-2 European Space Agency (ESA) satellites for the time period 1992 to 2000. Both methods involve choosing a master image from the database and creating a series of interferograms with respect to this image. The "Coherent Pixel Time Series" (CPTS) technique chooses pixels with good average coherence, aligns the unwrapped interferograms with a stable area and then performs an inversion to calculate the linear velocity to quantify the deformation. The Coherent Target Modeling (CTM) method calculates the temporal coherence of each pixel to identify stable targets and then determines the best velocity for each pixel by using a linear fit that maximizes the temporal coherence. Using these two methods we have been able to detect deformation on La Palma Island that has been previously undetectable by conventional InSAR methods. There is a roughly circular region on the Southern part of the island that is actively deforming at -4 to -8 mm/yr. This region is located near the Teneguia valcano, the host of the last known eruption on La Palma in 1971. A thorough investigation of the possible sources for this deformation revealed that it was most likely created by a subsurface thermal source

Geodetic and structural research in La Palma, Canary Islands, Spain: 1992-2007 results

We review the results of the geodetic and structural studies carried out on La Palma Island using geodetic and geophysical data during the period 1992–2007. InSAR and GPS observation techniques were applied to study the existence of deformation on the island and gravity observations were carried out for structural studies. Gravity data were inverted using a nonlinear three-dimensional gravity inversion approach to obtain the geometry of the anomalous bodies constructed in a random growth process with respect to an exponentially stratified background. The main structural feature is a large central body (under the Caldera de Taburiente) with high density, which was interpreted as the Pliocene-age uplifted seamount and a relatively dense intrusive plutonic complex/magma body. The Cumbre Vieja series is characterized by elongated minima distributed according to the rift structure. InSAR results show a clear subsidence located on the Teneguía volcano, where the last eruption took place in 1971. A thermal source is the most probable origin for this deformation. A GPS network composed of 26 stations covering the total island surface was set up. Vertical displacements determined comparing the GPS coordinates obtained in 2007 with coordinates determined in 1994 are consistent with the InSAR results obtained in the southern part of the island. This is not the case for the northern part. From the comparison of 2006 and 2007 coordinates it is clear that more time is needed to obtain significant displacements, but observed trends are also consistent with InSAR results. All the observed significant displacements are in stations located outside of the large high-density central body.Peer reviewe

The OGS–Northeastern Italy Seismic and Deformation Network: Current Status and Outlook

In this article, we describe the infrastructure developed and managed by the ItalianNational Institute of Oceanography and Applied Geophysics – OGS for the seismologicaland geodetic monitoring of northeastern Italy. The infrastructure was constituted inresponse to the ML 6.4 Friuli destructive earthquake of 1976, with the main mandateof supporting civil protection emergency activities.The OGS monitoring infrastructure is presently composed of a seismometric and astrong-motion network, complemented by a number of Global Navigation SatelliteSystems stations, each delivering observational data in real time, which are collectedand processed by the headquarters of the Center for Seismological Research of OGS inUdine. The OGS networks operate in close cooperation with Italian and internationalnetworks from neighboring countries, within the framework of the agreements forreal-time data exchange, to obtain improved rapid earthquake location and magnitudeestimations. Information regarding seismic events is released to the public through adedicated web portal and, since 2013, through social media.Aside from the standard monitoring activities ( > 30;000 events have been recordedsince 1976), the OGS has progressively increased the number of services to the publicand to the Civil Protection of the Friuli Venezia Giulia and Veneto regions. The highavailability of good quality data has resulted in the enhancement of scientific products,including advanced seismological studies of the area, spanning broadly from seismicsource characterization to engineering seismology.In the future, the OGS networks are expected to further contribute to the developmentof seismological research and monitoring infrastructures of the Central European region