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| Titel |
Four Years of Absolute Gravity in the Taiwan Orogen (AGTO) |
| VerfasserIn |
Maxime Mouyen, Frederic Masson, Cheinway Hwang, Ching-Chung Cheng, Nicolas Le Moigne, Chiung-Wu Lee, Ricky Kao, Nicky Hsieh |
| 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 |
250038458
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| Zusammenfassung |
| AGTO is a scientific project between Taiwanese and French institutes, which aim is to
improve tectonic knowledge of Taiwan primarily using absolute gravity measurements and
permanent GPS stations. Both tools are indeed useful to study vertical movements and
mass transfers involved in mountain building, a major process in Taiwan located
at the convergent margin between Philippine Sea plate and Eurasian plate. This
convergence results in two subductions north and south of Taiwan (Ryukyu and
Manilla trenches, respectively), while the center is experiencing collision. These
processes make Taiwan very active tectonically, as illustrated by numerous large
earthquakes and rapid uplift of the Central Range. High slopes of Taiwan mountains and
heavy rains brought by typhoons together lead to high landslides and mudflows
risks.
Practically, absolute gravity measurements have been yearly repeated since 2006 along a
transect across south Taiwan, from Penghu to Lutao islands, using FG5 absolute gravimeters.
This transect contains ten sites for absolute measurements and has been densified in 2008 by
incorporating 45 sites for relative gravity measurements with CG5 gravimeters.
The last relative and absolute measurements have been performed in November
2009.
Most of the absolute sites have been measured with a good accuracy, about 1 or 2 μGal. Only
the site located in Tainan University has higher standard deviation, due to the city
noise. We note that absolute gravity changes seem to follow a trend in every site.
However, straightforward tectonic interpretation of these trends is not valuable as
many non-tectonic effects are supposed to change g with time, like groundwater or
erosion. Estimating and removing these effects leads to a tectonic gravity signal,
which has theoretically two origins : deep mass transfers around the site and vertical
movements of the station. The latter can be well constrained by permanent GPS stations
located close to the measurement pillar. Deep mass transfers, on the contrary, must
be evaluated by modelling. Relative gravity, despite lower accuracy, enable us to
cover wider area (about 10Â 000Â km2). Our interest is thus to merge both types
of measurements to have a large overview of temporal g changes in the south of
Taiwan. |
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