Creepmeter

A creepmeter is an instrument that monitors surface displacement of an active fault. The accumulation of surface displacement may occur continuously (creep) or by sudden displacement events (seismically triggered) The Creepmeter Array in N-Chile which is part of the Integrated Plate Boundary Observatory (IPOC) is designed to record continuous or episodic displacement as well as sudden displacement events. The main goal of the study is to record a continous time-series of displacement across the faults to understand the mechanism of strain accumulation along crustal faults located in the Chilean Forearc above a highly active subduction zone. The first pilot instrument was installed in 2007 after the Tocopilla earthquake on Mejillones Peninsula. Today 11 instruments are continuously monitoring displacement accumulation across 4 target faults. Six of them transmit data continuously via satellite (BGAN, Inmarsat).

"Observing seismic and silent faulting related to a megathrust earthquake cycle" is a DFG funded project that is directly linked to processing and interpretation of the N-Chile creepmeter data.

People involved: This e-mail address is being protected from spambots. You need JavaScript enabled to view it (PI), This e-mail address is being protected from spambots. You need JavaScript enabled to view it (chief technician), This e-mail address is being protected from spambots. You need JavaScript enabled to view it , This e-mail address is being protected from spambots. You need JavaScript enabled to view it , Christoph Bach, This e-mail address is being protected from spambots. You need JavaScript enabled to view it , This e-mail address is being protected from spambots. You need JavaScript enabled to view it (PhD)

Setup
All the installed instruments use solid 12 mm thick invar rods as length standards, which are firmly attached to a concrete foundation on one side of the fault and pass through a PVC pipe to the far side of the fault. The creepmeters are buried at a depth of 30 - 70 cm, in order to increase the signal-to-noise ratio. We use a LVDT (linear variable differential transformer) with a range of 50 mm to monitor the relative displacement of the free end of the rod relative to the second fixation point. Displacement is converted to voltage change and stored on a data logger with a sampling rate of 2/min. In addition, a reference signal of 1 V is measured at the same sampling rate to correct for voltage fluctuations. Temperature at the rod is continuously measured to correct for thermal expansion and contraction of the length standard. The length of the instrument is dependent on the geometry at each site and ranges between 2 and 9 m. One station per target fault is also equipped with a weather station to control effects of humidity and air pressure changes. The time of each data logger is synchronised via GPS automatically.

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