IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS005 Oral Presentation 1917
Displacement-length scaling relations of normal faults and
paleoearthquakes in the active Taupo Rift, NEW ZEALAND
Prof. John Walsh
Fault Analysis Group,School of Geological Sciences University College Dublin IASPEI
A. Nicol
The relation between maximum displacement and length provides important information about the
scaling properties of faults and earthquakes. Displacement-length plots typically reveal slopes of 1-1.5
for ancient fault systems and 1 for historical earthquakes. Active normal faults in the Taupo rift,
however, have slopes of 0.5-0.7 for paleoearthquakes and faulted volcanic surfaces ranging up to ca. 60
ka in age. These low slopes are attributed to two principal factors: sampling bias and fault
interaction/intersection. The bulk of our data are from a digital elevation model of displaced geomorphic
surfaces with a vertical resolution of ~2 m. Displacements less than ~2 m are not routinely imaged in
the model resulting in an under-sampling of small faults and a reduction in lengths of at least 100-200
m. Both of these sampling artefacts introduce a systematic under-sampling of low displacement-length
faults particularly for those faults with lengths of