HR: 16:00h
AN: G14A-01 INVITED     [Abstracts]
TI: `Geologic time series' of earth surface deformation
AU: * Friedrich, A M
EM: anke@alum.mit.edu
AF: Institute of Geosciences, University of Potsdam, Karl-Liebknechtstr. 24, Golm, 14476 Germany
AB: The debate of whether the earth has evolved gradually or by catastrophic change has dominated the geological sciences for many centuries. On a human timescale, the earth appears to be changing slowly except for a few sudden events (singularities) such as earthquakes, floods, or landslides. While these singularities dramatically affect the loss of life or the destruction of habitat locally, they have little effect on the global population growth rate or evolution of the earth's surface. It is also unclear to what degree such events leave their traces in the geologic record. Yet, the earth's surface is changing! For example, rocks that equilibrated at depths of > 30 km below the surface are exposed at high elevations in mountains belts indicating vertical motion (uplift) of tens of kilometers; and rocks that acquired a signature of the earth's magnetic field are found up to hundreds of kilometers from their origin indicating significant horizontal transport along great faults. Whether such long-term motion occurs at the rate indicated by the recurrence interval of singular events, or whether singularities also operate at a higher-order scale ("mega-singularities") are open questions. Attempts to address these questions require time series significantly longer than several recurrence intervals of singularities. For example, for surface rupturing earthquakes (Magnitude > 7) with recurrence intervals ranging from tens to tens of thousands of years, observation periods on the order of thousands of years to a million years would be needed. However, few if any of the presently available measurement methods provide both the necessary resolution and "recording duration." While paleoseismic methods have the appropriate spatial and temporal resolution, data collection along most faults has been limited to the last one or two earthquakes. Geologic and geomorphic measurements may record long-term changes in fault slip, but only provide rates averaged over many recurrence intervals. Space-geodetic measurements provide high-resolution time series of contemporary surface deformation, but most systems have been recording for less than ten years (GPS data), and the spatial coverage is only beginning to improve (e.g., InSAR data). Assuming that we are not willing to wait hundreds of years of global geodetic recording, what would be our most realistic options for collecting appropriate data in the near future?
DE: 8107 Continental neotectonics
DE: 1208 Crustal movements--intraplate (8110)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting