Christopher W. Fuller

Erosion rates and orogenic-wedge kinematics in Taiwan inferred from fission-track thermochronometry

New apatite and zircon fission-track ages and previously published thermochronometric data are used to evaluate erosion rates and particle paths within the active Taiwan arc-continent collision. We present 20 new apatite fission-track ages and 6 new zircon fission-track ages. Apatite and zircon ages are all reset in the northern and eastern parts of Taiwan, although the region of reset apatite ages is larger. We interpret this pattern as resulting from crustal accretion at the western margin of the orogenic wedge combined with southward propagation of the collision zone. A onedimensional thermal model including erosion provides prediction of the fission-track ages. The distribution of reset ages is best explained with an erosion rate of 4‐6 mm/yr. Given a propagation velocity of 60 mm/yr, this erosion rate implies that nearly 25 km of material has been eroded from northern Taiwan. The lack of reset 40 Ar/ 39 Ar ages from muscovite and biotite suggests that rockparticle paths have a large horizontal component, a result consistent with an eroding orogenic-wedge model.

Formation of forearc basins and their influence on subduction zone earthquakes

Recent observations of an association between forearc basins and slip during subduction thrust earthquakes suggest a link between processes controlling upper plate structure and seismic coupling on the subduction-zone thrust fault. We present a mechanism for the formation of these basins where sedimentation occurs on landward-dipping segments of the subduction wedge, which itself is actively growing through the accretion of material from the subducting plate. Our numerical simulations demonstrate that sedimentation stabilizes the underlying wedge, preventing internal deformation beneath the basin. Maximum slip during great-thrust earthquakes tends to occur where sedimentary basins stabilize the overlaying wedge. The lack of deformation in these stable regions increases the likelihood of thermal pressurization of the subduction thrust, allows the fault to load faster, and allows greater healing of the fault between rupture events. These effects link deformation of the subduction wedge to the seismic coupling of the subduction thrust.

Erosion rates for Taiwan Mountain Basins: New determinations from suspended sediment records and a stochastic model of their temporal variation

We estimate erosion rates from suspended sediment records for 11 basins in the eastern Central Range (ECR) of Taiwan using methods based on mean measured sediment discharge, a rating curve of sediment and water discharge, and a rating curve corrected for periods of limited sediment due to the lack of landslide‐supplied sediment. The preferred method for any basin depends on record length and sampling frequency, with higher quality records being analyzed by the latter method. Erosion rate estimates range from 2.2 to 8.3 mm/yr for records with varying sampling frequencies and durations between 8 and 27 yr. This variation in erosion rates does not seem to reflect lithology, tectonic environment, or climate. We interpret the variation in terms of natural stochastic variation in water discharge and sediment supply. To assess the quality of the erosion rate estimates and to better understand the dependence of uncertainty on the duration and frequency of sampling, we construct a stochastic model of sediment supply and transport for the Chihpen River of the ECR. The model stochastically predicts the water discharge and sediment supply from landslides and calculates the transport of suspended sediment through application of a deterministic transport law. We determine that with a 27‐yr hydrograph with 780 suspended sediment load measurements for the Chihpen River, assuming an erosion rate of 5.1 mm/yr, there is a 68.3% probability of determining an erosion rate within \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Computational Tools for Low-Temperature Thermochronometer Interpretation

\pm 2.7/ 4.0

The Formation of Forearc Basins and Their Context in Active Margin Structure

\end{document} mm/yr of the actual erosion rate. We provide an estimate of the uncertainty associated with various sampling frequencies and record lengths and find that it is difficult to push uncertainties below ±2 mm/yr.

Process Based Explanations for Correlations Between the Structural and Seismic Segmentation of the Cascadia Subduction Wedge

Bulk cash smuggling is a serious issue that has grown in volume in recent years. By building on the magnetic characteristics of paper currency, induction sensing is found to be capable of quickly detecting large masses of banknotes. The results show that this method is effective in detecting bulk cash through concealing materials such as plastics, cardboards, fabrics and aluminum foil. The significant difference in the observed phase between the received signals caused by conducting materials and ferrite compounds, found in banknotes, provides a good indication that this process can overcome the interference by metal objects in a real sensing application. This identification strategy has the potential to not only detect the presence of banknotes, but also the number, while still eliminating false positives caused by metal objects.