Abstract
Our understanding of the internal dynamics of the Earth is largely based on images of seismic velocity variations in the mantle obtained with global tomography. However, our ability to image the mantle is severely hampered by a lack of seismic data collected in marine areas. Here we report observations made under different noise conditions (in the Mediterranean Sea, the Indian and Pacific Oceans) by a submarine floating seismograph, and show that such floats are able to fill the oceanic data gap. Depending on the ambient noise level, the floats can record between 35 and 63% of distant earthquakes with a moment magnitude M≥6.5. Even magnitudes <6.0 can be successfully observed under favourable noise conditions. The serendipitous recording of an earthquake swarm near the Indian Ocean triple junction enabled us to establish a threshold magnitude between 2.7 and 3.4 for local earthquakes in the noisiest of the three environments.
Highlights
Our understanding of the internal dynamics of the Earth is largely based on images of seismic velocity variations in the mantle obtained with global tomography
The full control over the recording strategy offered by the two-way communication makes the MERMAID a highly flexible recording instrument and contrasts it drastically with the ocean bottom seismometers (OBSs) and moored hydrophones
The MERMAID drifts passively, typically with a speed of several km per day, until an earthquake signal is detected. If this is identified as a strong P wave, the MERMAID ascends for transmission of the recorded waveform as well as its global positioning system (GPS) coordinates at the surface
Summary
Our understanding of the internal dynamics of the Earth is largely based on images of seismic velocity variations in the mantle obtained with global tomography. We report observations made under different noise conditions (in the Mediterranean Sea, the Indian and Pacific Oceans) by a submarine floating seismograph, and show that such floats are able to fill the oceanic data gap. Considering that about 70% of the Earth is covered by water, advances in seismic monitoring and imaging of the Earth’s mantle via seismic tomography depend critically on the development of radically new instruments, capable of providing seismic data at significantly lower cost. Simons et al.[5,6] proposed such a new instrument, known as MERMAID (Mobile Earthquake Recording in Marine Areas by Independent Divers), that is a submarine buoyancy-matched float equipped with a hydrophone to detect acoustic signals generated when seismic waves from the Earth’s interior refract into the water column at the sea bottom. In this work we report on the final development of an autonomously functioning MERMAID7, capable of recognizing earthquake waves and transmitting seismograms in quasi-real time
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
