ACTIVE TECTONICS AND PALEOSEISMOLOGY GROUP
HIGH PRECISION LEVELINGS
Recent vertical movements profile between Alicante and Almeria, obtained between 1934 and 1976 (Giménez et al, 2000).
The comparison of the relative position between topographical
vertexes in different epochs allows us to calculate the cortical deformation
rates in active zones. High precision leveling (HPL) data allows us to
determine recent vertical movements with millimetric precision. From the
HPL data obtained by the IGN in the last 125 years we have obtained significant
deformations in the East of the Iberian Peninsula. A new line of HPL data
was established and measured in 1997 to monitor the vertical deformations
between Guardamar de Segura and Alicante.
GLOBAL POSITIONING SYSTEM
The comparison of the relative position between geodetical
vertexes of a network in different epochs enables us to calculate the cortical
deformation rates in active zones. The measurements of geodetical networks
by means of GPS allows us to determine the horizontal variation of the
position between the vertexes with subcentimetric precision. The CuaTeNeo
GPS network , consisting of 15 monuments, was set up to monitor the horizontal
crustal deformations in the provinces of Almería and Murcia (Alhama
de Murcia, Palomares and Carboneras fault system). The first campaign (CuaTeNeo
epoch 0) was carried out in 1997.
REGIONAL AND DETAILED GEOMORPHOLOGY
Active fault in the western margin of Salar Grande(Atacama Desert, Chile).
The recent tectonic activity of an area can be characterized
in a first approach by studding the regional geomorphology. Some morphological
features observed in young sediments indicate the presence of recent activity
such as fault scarps, deformed alluvial fans, river channels with disequilibrium
etc. This kind of studies are done mainly by topographic, aerial photographs,
satellite and field analysis.
Geomorphology in a more detailed scale is also useful
for determining the interaction between events of deformation and deposition
of sedimentary surface units and for proper selection of trenching sites
Microtopography is a powerful tool for describe with
high precision the surface of the analyzed area and thus perform quantifications
on the vertical or horizontal slip, the distribution of surficial sedimentary
units etc...Topographic leveling by profiling across the target fault enables
the quantification of the amount of surface deformation produced by the
fault. Detailed topographic maps in specific areas allows precise mapping
of surface units and thus better selection of trench sites.
|Trench in El Camp fault (NE Iberian Peninsula). |
Trenching analysis across or near a faulted surface is
one of the best ways to detect individual events of paleoearthquakes and
to characterize the seismogenic behavior of the causative fault, that is
to perform a paloseismological analysis. Detailed logging of the trench
outcrop and study of the cross section are performed. The selection of
a proper site where to trench and the availability of samples suitable
to be dated and situated in the best position are key points in such an
analysis. Trenching, and paleoseismological results, are always the final
step of a broader analysis that considers all scales, from the regional
geomorphological analysis to the detailed sedimentological observations
made during the site selection step. the results of a paleoseismological
study may contribute to better constrain the seismic hazard of a specific
fault with data such as: slip rate, recurrence period, elapsed time, slip
per event and maximum earthquake as well as the geometry of the seismogenic
Maintained by H. Perea
Last updated: 26 April 2002.