Monitoring methane emission of mud volcanoes by seismic tremor measurements: a pilot study

Abstract

Abstract.A new approach for estimating methane emission at mud volcanoes is here proposed based on measurements of the seismic tremor on their surface. Data obtained at the Dashgil mud volcano in Azerbaijan reveal the presence of energy bursts characterized by well-determined features (i.e. waveforms, spectra and polarization properties) that can be associated with bubbling at depth. Counting such events provides a possible tool for monitoring gas production in the reservoir, thus minimizing logistic troubles and representing a cheap and effective alternative to more complex approaches. Specifically, we model the energy bursts as the effect of resonant gas bubbles at depth. This modelling allows to estimate the dimension of the bubbles and, consequently, the gas outflow from the main conduit in the assumption that all emissions from depth occur by bubble uprising. The application of this model to seismic events detected at the Dashgil mud volcano during three sessions of measurements carried out in 2006 and 2007 provides gas flux estimates that are in line with those provided by independent measurements at the same structure. This encouraging result suggests that the one here proposed could be considered a new promising, cheap and easy to apply tool for gas flux measurements in bubbling gas seepage areas.

Insight Into Campi Flegrei Caldera Unrest Through Seismic Tremor Measurements at Pisciarelli Fumarolic Field

“…During this episode, the seismicity was characterized by short‐lived impulsive transients (Figure ). Similar transients, recorded at the Dashgil mud volcano in Azerbaijan, are described by Albarello et al () as associated with methane bubbling. Microevents, defined as short‐duration events, have been also recorded by ocean bottom seismometers (OBS) deployed over soft sediments in the western part of the Sea of Marmara (Turkey).…”

Character of seismic motion at a location of a gas hydrate‐bearing mud volcano on the SW Barents Sea margin

“…These models include oscillations of large magma bodies, cracking processes, excitation and resonance of fluid‐filled cracks, fluid flow‐induced oscillations of conduits, and bubble oscillation due to hydrothermal boiling. The bubbling processes are also an important behavior of the mud volcanism [ Albarello et al ., ]. Occurrence of harmonic tremors is reported in areas without any volcanic activity and can be linked to gas venting [ Pontoise and Hello , ] or to the resonant excitation in fluid‐filled cracks due to hydrothermal circulation [ Díaz et al ., ].…”

“…The study of submarine mud volcanos received increased interest in the last decades as their presence might be linked to deep‐seated petroleum systems [ Milkov , ; Dimitrov , ; Albarello et al ., ]. Thus, they may indicate potential windows to deeper hydrocarbon resources [e.g., Planke et al ., ; Milkov , ].…”

Observing Volcanoes from the Seafloor in the Central Mediterranean Area

“…These non-earthquake signals are impulsive and have a very short duration, and they are often called Short Duration Events (SDE). Non-earthquake seismic signals containing low energy and high frequency have also been observed by D'Alessandro et al [64], classified as SDE, and associated with hydrothermal activity at MS. SDEs have been previously observed both in submarine in hydrothermal systems (e.g., [74]) and on land in the proximity of mud volcanoes [75]. A first type of SDE recorded at MS with the seafloor observatories has a frequency spectrum from about 5 Hz-50 Hz (seismometer Nyquist frequency), is monochromatic, with a sharp onset and a very short duration (about 0.5 s; Figure 5).…”