Duration - 01/03/2000 - 28/02/2003
Funding - New Zealand Royal Society, Marsden Fund
Co-ordinator - Dr Andy Nicol
Research Partners
Basic Aims
The earth's crust is often broken up by normal faults which grow during repeated catastrophic earthquakes over millions of years. Exactly how individual earthquakes sum to produce the final fault patterns is poorly understood. To address this question this project aims to chart the development of a normal-fault system from the Taupo Volcanic Zone, New Zealand, using detailed digital topography and precise ages from volcanic deposits. These data will allow us to relate fault growth during earthquakes to the long term (e.g. >20 thousand years) development of faulting.
In many regions of the world the earth's crust is broken up by normal faults which grow and accumulate displacement during catastrophic earthquakes. Large cumulative fault displacements accrue during many earthquakes over millions of years but the systematics of this process are not well understood. Studies of historical earthquakes from throughout the world indicate that fault slip increases with fault dimension (e.g. Wells & Coppersmith 1994), while recurrence models for the largest earthquakes on a given fault typically describe some form of periodic behaviour (Schwartz & Coppersmith 1984, Lindvall et al. 1989, Berryman & Beanland 1991). Similarly, data from inactive fault systems indicate that cumulative maximum displacements increase with increases in fault length (e.g. Walsh & Watterson 1988, Cowie & Scholz 1992). Recent work also suggests that when averaged over a million years or more long term fault displacement rates are constant and strongly dependent on size with large faults moving faster than small (Nicol et al. 1997). The earthquake and long term geological data clearly share some common systematic elements but there are also significant inconsistencies. To obtain short and long term growth histories for normal faults requires active faulting at the ground surface, preservation of syn-faulting horizons and precise age control for offset surfaces spanning a significant portion of the life of the faults. These conditions require a delicate balance to be maintained between the rates of sedimentation, erosion, regional tectonic uplift and fault displacement. The Taupo Volcanic Zone in New Zealand is one of the few places in the world where these conditions are met and offers an excellent opportunity for comparing earthquake faulting with longer-term fault growth.
Contact: John Walsh
Tel: +353 1 716 2169
Email