Ocean-Bottom distributed acoustic sensors: new tools for underwater seismology
One of the greatest outstanding challenges in seismology is the sparsity of instrumentation across Earth’s oceans. Poor spatial coverage results in biases and low-resolution regions in global tomography models as well as significant location uncertainty for offshore seismicity. Also, the lack of significant seismic instrumentation offshore makes it more complicated to have reliable early warning systems capable of mitigating some of the disastrous consequences of tsunamis. Ocean-bottom seismometers (OBS) are indeed available, but they are generally very expensive and limited by rapid data telemetry and battery life except in near-shore environments. The aim of this proposal is to provide a low-cost deployable solution (basically inexistent so far) for monitoring seismicity in remote areas of the ocean. The idea would be to retrofit existing telecommunication optical fiber cables lying in the ocean and transform them (with no basic change in the cable itself) into powerful seismic sensing arrays. With a single optoelectronic unit in the end of the cable (onshore), a full span of 50 km or more could be monitored, with thousands of measuring points interrogated. The proposed solution would be much cheaper than current alternatives and could easily allow deploying a large number of these sensor arrays, particularly in currently unmonitored areas. Moreover, all the fibre-optic cables used worldwide for communications are suitable for our proposed sensor, hence the same installation methodology could be exported to a large number of scenarios. The proposed solution has been pinpointed by prestigious seismology laboratories worldwide (Caltech Seismology Lab, GFZ Postdam, GeoAzur Nice) as a system with a great potential for adoption in the seismological field. A suitable demonstrator will be developed along the project and will be field tested in collaboration with GeoAzur Nice, in an underwater cable in the coast of Greece.