Earthquake detection
A subsea well scenario has been established in laboratory The test set-up was designed such that different losses and reflection levels (between the lead-in fibre and sensor fibre) can be simulated by adjusting three separate variable optical attenuators (VOA) in a connectors simulator. The length of the lead-in fibre is 14.2 km followed by a 6.1 km long standard sensing fibre.
Another earthquake has been recorded with an operational telecom cable. An earthquake (1200 km away) of magnitude 4.5 was recorded along the cable positions 35 – 80 km from the onshore interrogator (cable direction is close to that of the seismic wave). The peak recorded amplitude was about 15 pico-strain.
