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| Titel |
Ocean tide loading effects on new gravity tide measurements made at south of Spain |
| VerfasserIn |
José Arnoso, Maite Benavent, Fuensanta G. Montesinos |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250035948
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| Zusammenfassung |
| Tidal gravity observations have been made recently in Algodonales (ALG) site located in the
region of Andalucía, at the south of Spain. Other former gravity tide observations around this
region were made in Granada and San Fernando (Vieira et al., 1983), which are 165 km
northeast and 85 km southwest distant from ALG, respectively. It is planned to make shortly
new gravity measurements in Melilla, which is a Spanish city placed at the other side
of the Strait of Gibraltar (north of Morocco). In this way, we will dispose of an
interesting gravity profile for studying the elastic response of the Earth at tidal periods in
this important area of geodynamic activity. In fact, this broad region is situated
around the interaction area of the Eurasia and Africa plates, where various geological
structures are present, as the Alboran Sea basin, the Betico-Rifean chain, the Gulf of
Cádiz and the Atlas mountain range. Also, the area is affected by occurrence of
moderate magnitude earthquakes, mostly focused at shallow and intermediate depths (<
40 km) although exist records of very deep earthquakes located at the south of
Granada. The two tectonic plates that interact have different movements slightly, which
originates an accumulation of efforts in the fault line, that contributes to the earthquake
occurrence in the zone (see e.g. Stich et al., 2006; Buforn et al., 2004; Fullea et al.,
2006).
The gravity observations made in ALG site, which is situated about 55km far from the
coast, are considerably affected by ocean tide loading produced by the effect of the nearest
Atlantic Ocean and Mediterranean Sea. Thus, the gravity effect induced by the ocean masses
contributes up to 9% of the observed signal, for the main tidal constituents. The ocean
loading effects have been calculated following the Farrell’s (1972) procedure through the
convolution between gravity Green’s functions and the ocean tide distribution given by global
oceanic models (TPXO7.1, FES2004, GOT00, GOT4.7,..). To improve the loading
predictions in the area, we have used the recently developed regional oceanic model named
IBER01 (Benavent et al., 2009). The model was constructed by assimilating satellite
altimeter data and tide gauge measurements into a hydrodynamic model and is
extended through the domain given by 48Ë .0N to 34Ë .0N and 6Ë .0E to 16Ë .0W,
having a resolution of 5′Ã5′. Thus, the contribution of IBER01 to the tidal loading
calculated at ALG site represents about 72% and 55% of the total load for semidiurnal
and diurnal waves, respectively. Results obtained show that precise calculations of
ocean tide loading improves the interpretation of the gravity tide models obtained in
the area and also allow us to assess the efficiency of the global oceanic models
around the Strait of Gibraltar where the Mediterranean and Atlantic waters converge. |
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