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Abstract:
We introduce a Distributed Acoustic Sensing (DAS) array deployed for one month between February and March 2023 and which utilized ~25 km-long telecommunication fibers running roughly parallel and perpendicular to the Alpine Fault near Haast. A key goal of this DAS deployment and planned further work is to improve characterization of natural hazards in southern New Zealand including Alpine Fault seismicity and rockfalls, and to demonstrate the feasibility of DAS studies using dark commercial telecommunications fibers in New Zealand. DAS, with its high spatial (~1 m) and temporal (1 kHz) resolutions, can improve the detection of weak seismic sources, including low-magnitude earthquakes diagnostic of fault activity, rockfalls and avalanches in remote mountainous region, and sediment transport in river systems. The dense sensor deployment across the Alpine Fault further allows us to make high-resolution images of the fault zone including the near-surface fault geometry and velocity structure across the Alpine Fault where it crosses the sole highway in the area. The DAS acquisition was scheduled to coincide with the operation of the ~450 km-long Southern Alps Long Skinny Array (SALSA), which includes 45 mostly broadband seismometers installed 10–12 km apart within ~3 km of the fault trace, to provide new opportunities for interpreting DAS and conventional seismometer data to study seismicity and fault geometry.
