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Poster Abstracts
colonies would be characterized in terms of how they appeared (colour and texture), and isolated to try to genetically identify
them. We found that microorganisms do live in the mud, but with the agar we used very few culturable organism came to
fruition. We were unable to genetically identify them as their DNA was not amplified. The next steps of the project are to
continue trying to amplify the DNA for genetic analysis, perhaps using different methods. Also, using different types of agar
plates to plate the mud on to see if different types of organisms appear instead of the small set obtained. It would be
interesting to use media with higher sulfur and salt concentrations, as this was prominent in the environment.
THREE-DIMENSIONAL MODELING OF INTERSEISMIC DEFORMATION IN TAIWAN (A-055)
B. Rousset, S. Barbot, J.P. Avouac, Y.J. Hsu, and J.C. Lee
The Taiwan Island, a complex orogenic system at the intersect between an arc-continent collision and a subduction zone, is a
much studied area. The 1999 Chi-Chi earthquake, the latest of a series of Mw 7+ earthquakes, was a reminder of the active
tectonics shaping the island. Yet, the structure of the fault system at crustal depths, responsible for the sequence of devastating
earthquakes, is not fully resolved. In this study, we establish the fault structure of Taiwan in its entirety that reconciles many
geophysicals observations (seismicity, tomography and structural analyses) and explains the pattern of secular deformation.
We optimise and complement the fault geometry at crustal depths using data from several GPS networks, including islandwide
continuous measurements and regional campaigns. The inversion of the entire velocity field in Taiwan can be
challenging because a large portion of the convergence is taking place on deep décollements, far below the surface, for which a
precise geometry is unknown. We develop a new inversion scheme where we use the difference between nearby GPS stations
to constrain slip rate on faults. We show that the method allows for a much finer optimization of fault geometry and is
particularly fitted for a complex faulting environment such as Taiwan. We find that the Chihshang segment of the
Longitudinal Valley Fault is sliping at a rate of ~30 mm.yr-1 whereas the Yumei segment to the north appears locked. The
Chelungpu Fault and the Shuangtung Fault also appear locked, but the décollement subjacent is inferred to move at a rate of
20 to 30 mm.yr-1. The Chuckou system, which originated 10 earthquakes of Mw 6+ in the past 100 years seems locked at the
surface and loaded from below at a rate of ~20 mm.yr-1. The Hsincheng fault, 50 km to the south of Taipei seems loaded from
below at a rate of 12 mm.yr-1. The GPS data alone are not sufficient to determine uniquely the degree and area of locking and,
but if completely locked, such a fault could host an earthquake of Mw 6.2 with a recurrence time of ~40 yr. The integration of
decades of GPS surveys, previous fine-scale structural analyses, seismic and tomography imaging allows for a refined threedimensional
fault structure for Taiwan. Our study reveals areas under active loading, which could represent substantial
seismic hazards around the regions of Hualien, Jhudong, Fongyuan and Chiayi.
PROBABILISTIC ASSESSMENT OF BUILDING RESPONSE TO SIMULATED AND RECORDED GROUND
MOTIONS (B-088)
K.L. Rowe and A.B. Liel
This study examines the seismic response of buildings subjected to both physics-based ground motion simulations and
recorded ground motions time histories. Nonlinear dynamic analysis is used to evaluate the response of six archetypical
reinforced concrete (RC) frame buildings to a set of three simulated and three recorded earthquakes. Using probabilistic
analysis, building response is examined and statistically compared to determine whether the broadband ground motion
simulations and the recorded ground motion time histories yield similar distributions for building response, focusing
especially on the likelihood of earthquake induced collapse. Important aspects of the ground motion time histories that may
cause differences in building response are then examined to attempt and explain the source of these dissimilarities in response.
This study also examines the potential of applying the probabilistic analysis outlined in this study to the broader area of
seismic risk analysis by using response results from recorded or simulated ground motions to predict regional collapse risks.
This offers a new framework with which to evaluate building vulnerability to seismic events. Results indicate that, when
examined based on the elastic spectral response, there are significant differences in building response. These differences are
attributed in part to the long-period energy (T>1sec) content of the ground motions, and can be captured if ground motion
intensity is quantified in terms of inelastic spectral displacement. Higher mode effects, earthquake duration, energy content
and rate of energy accruement were not found to have a significant effect on differences in building response.
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