Magmatic intrusions in real time

Abstract

Conventional geodetic techniques — such as electronic distance measurements, borehole strainmeters, tilt measurements and satellite-based methods — lack the spatiotemporal resolution needed to resolve rapid magma intrusion dynamics, such as the evolution and emplacement of magma volume in real time.

To address this issue, Li and colleagues deployed a distributed acoustic sensor in Keflavík and converted a 100-km-long telecommunication fibre cable — running along the coastline from Keflavík through Grindavík — into a sensing array with 10,000 recording channels. The system contained a low-pass filter with a 0.01-Hz cutoff frequency and a spatial median filter to remove common-mode noise. As magma deforms the Earth’s crust, it alters the phase of the scattered light propagating through the fibre. By analysing these phase shifts across the channels, the sensing set-up could track strain rates and map subsurface magma migration in real time.