 |
| Titel |
Continuous catchment-scale monitoring of geomorphic processes with a 2-D seismological array |
| VerfasserIn |
A. Burtin, N. Hovius, D. Milodowski, Y.-G. Chen, Y.-M. Wu, C.-W. Lin, H. Chen |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250069058
|
|
|
|
|
|
| Zusammenfassung |
| The monitoring of geomorphic processes during extreme climatic events is of a primary
interest to estimate their impact on the landscape dynamics. However, available techniques to
survey the surface activity do not provide a relevant time and/or space resolution.
Furthermore, these methods hardly investigate the dynamics of the events since their
detection are made a posteriori. To increase our knowledge of the landscape evolution and
the influence of extreme climatic events on a catchment dynamics, we need to develop new
tools and procedures. In many past works, it has been shown that seismic signals are
relevant to detect and locate surface processes (landslides, debris flows). During the
2010 typhoon season, we deployed a network of 12 seismometers dedicated to
monitor the surface processes of the Chenyoulan catchment in Taiwan. We test the
ability of a two dimensional array and small inter-stations distances (~ 11 km) to
map in continuous and at a catchment-scale the geomorphic activity. The spectral
analysis of continuous records shows a high-frequency (> 1 Hz) seismic energy that is
coherent with the occurrence of hillslope and river processes. Using a basic detection
algorithm and a location approach running on the analysis of seismic amplitudes,
we manage to locate the catchment activity. We mainly observe short-time events
(> 300 occurrences) associated with debris falls and bank collapses during daily
convective storms, where 69% of occurrences are coherent with the time distribution of
precipitations. We also identify a couple of debris flows during a large tropical
storm. In contrast, the FORMOSAT imagery does not detect any activity, which
somehow reflects the lack of extreme climatic conditions during the experiment.
However, high resolution pictures confirm the existence of links between most
of geomorphic events and existing structures (landslide scars, gullies-¦). We thus
conclude to an activity that is dominated by reactivation processes. It highlights
the major interest of a seismic monitoring since it allows a detailed spatial and
temporal survey of events that classic approaches are not able to observe. In the
future, dense two dimensional seismological arrays will assess in real-time the
landscape dynamics of an entire catchment, tracking sediments from slopes to rivers. |
|
|
|
|
|
|