What does a continental transform fault look like ahead of a major earthquake? Results from the first phase of the DFDP drilling project, Alpine Fault, New Zealand
Associate Professor, Victoria University of Wellington
- Date & Time
- Building 3, Room 3240 (main USGS conference room)
- David Shelly
Understanding the physical conditions prevailing in a fault zone immediately prior to a large earthquake would provide primary observational constraints on processes operating at different times and on different scales during the seismic cycle. The almost 300 years that have elapsed since the last Alpine Fault earthquake (MW~7.9 in 1717 CE) constitute a large fraction of the fault's 200-400 year average recurrence interval. In other words, the Alpine Fault appears to be late in the cycle of stress accumulation that will ultimately result in another large earthquake. The first phase of the Deep Fault Drilling Project (DFDP-1) was completed in early 2011 with the drilling at Gaunt Creek of two boreholes intersecting the shallow Alpine Fault. Core samples, wireline logging data, and hydraulic measurements document ambient conditions and fault zone structures at 0.1-100 m scales and enable us to describe the conditions under which the next Alpine Fault earthquake will occur. In this talk, I will discuss key characteristics of the individual DFDP-1 data sets and related observations, and their combined implications for fault zone evolution and deep structure.