Volcanic tremor and plume height hysteresis from Pavlof Volcano, Alaska

Abstract

Abstract:The March 2016 eruption of Pavlof Volcano, Alaska produced ash plumes that canceled over 100 flights in North America. The eruption produced strong tremor recorded by seismic and remote low-frequency acoustic (infrasound) stations, including the EarthScope Transportable Array. The relationship between the tremor amplitudes and plume height changes considerably between the waxing and waning portions of the eruption. Similar hysteresis has been observed between seismic river noise and discharge during storms, suggesting flow and erosional processes in both rivers and volcanoes can produce irreversible structural changes detectable in geophysical data. We propose that the time-varying relationship at Pavlof arose from changes in the tremor source related to volcanic vent erosion. This relationship may improve estimates of volcanic emissions and characterization of eruption size and intensity. One Sentence Summary:The relationship between volcanic tremor and plume height changes during the waxing and waning portions of the eruption. Main Text:There are a number of well-documented challenges in monitoring volcanic eruptions and their associated hazards (e.g. 1, 2). Observatories typically rely on local seismic networks and satellites to make critical decisions about eruption size and intensity. However, seismic networks can be sparse and difficult to maintain, particularly at remote volcanoes like those in the Aleutian Islands. Satellites often have limited spatial and temporal resolution and may be inhibited by cloud cover. Other remote geophysical methods, such as infrasound (low frequency acoustic) arrays, can provide unique and detailed information on eruption processes (e.g. 3), but may also be part of a sparse network and have limited signal-to-noise ratio (SNR) and latency due to the propagation distance. It is therefore a priority to integrate multiple observations to assess the eruptive hazards during crisis response. However, we currently lack the ability to quantitatively link seismo-acoustic observations to the intensity of ash emissions.Seismic and infrasonic volcanic tremor is the continuous vibration of the ground and air, respectively, from a volcano. The origin of volcanic tremor is a subject of active research, with attempts to understand its relation to fluid transport in the solid earth and atmosphere (e.g. 3, 4). Volcanic tremor during a sustained eruption is termed eruption tremor. Models of seismic eruption tremor include a downward vertical force on the Earth in response to volcanic jet thrust (5), erosion of the volcanic conduit and vent (6), and chaotic wagging of a magma column (7). Infrasonic tremor during eruptions has been compared to the noise from high velocity, turbulent jet flows (8) and longer period oscillations are modeled as the result of the emplacement and oscillation of the plume (9).However, these models do not explain all features of eruption tremor, and do not currently provide accurate estimates of critical eruption source parameters, such as mass flux and plume h...

Forecasting the Eruption of an Open‐Vent Volcano Using Resonant Infrasound Tones

“…Volcano monitoring makes use of continuous infrasound measurements (sound below 20 Hz) for understanding the dynamics of eruptions ranging from small to large (Fee & Matoza, ) and for a wide range of mechanisms, including explosions (Johnson & Miller, ; Morrissey & Chouet, ), gas jetting (Matoza et al, ), and surface mass movements like pyroclastic flows and lahars (Johnson & Palma, ; Yamasato, ). Infrasound studies have proven useful in remotely quantifying eruption parameters (Fee et al, ; Woulff & McGetchin, ); however, until present, there has been limited application and understanding of how to use infrasound to identify eruption precursors.…”

Space‐Time Evolution of Magma Storage and Transfer at Mt. Etna Volcano (Italy): The 2015–2016 Reawakening of Voragine Crater

“…The study of these signals can shed light on the structure of the shallower portions of plumbing system (Chouet & Matoza, 2013, and references therein), on the magmatic intrusions (e.g., Tarasewicz et al, 2014), and on processes taking place within the plumbing system, such as pressurization and depressurization (e.g., Cannata et al, 2015). Indeed, it has been used to provide information about the geometry of the uppermost portions of the plumbing system (e.g., Sciotto et al, 2013), to investigate its modifications during the eruptions (Fee et al, 2017), as well as to reconstruct the evolution of the eruptive (especially explosive) activities (e.g., Ripepe et al, 2013). Indeed, it has been used to provide information about the geometry of the uppermost portions of the plumbing system (e.g., Sciotto et al, 2013), to investigate its modifications during the eruptions (Fee et al, 2017), as well as to reconstruct the evolution of the eruptive (especially explosive) activities (e.g., Ripepe et al, 2013).…”

Infrasound Signal Detection and Back Azimuth Estimation Using Ground‐Coupled Airwaves on a Seismo‐Acoustic Sensor Pair

“…Since our method relies on time shifting the data, if the sensors are deployed at less than a dt equivalent distance, then all the time shifts will be subsample rate. With sub‐ dt equivalent sensor spacing an accurate back azimuth is not feasible, but an evaluation of the seismo‐acoustic coherence is still a valuable tool as it can be used to distinguish GCAs and acoustic waves in the seismic record (Fee et al, ; Matoza & Fee, ). We recommend a sensor spacing of at least a dt equivalent, if not several, and as high a sample rate as is feasible.…”

“…The examples of GCAs in this manuscript and in Matoza and Fee () are higher in frequency, above 5 Hz. There are, however, examples of energy at lower frequencies, such as the recent Pavlof Volcano eruption where there was coherence from ~0.8 to 8 Hz (Fee et al, ). In general, the frequency characteristics of GCAs reflect those of the incident airwave (Edwards et al, , ).…”

“…A frequently observed phenomenon in infrasonic wave propagation is when an incident acoustic wave traveling through the atmosphere encounters the Earth's surface and part of the wave energy is transferred to the ground as a seismic wave, known as a ground‐coupled airwave (GCA). GCAs from a variety of sources including volcanoes, bolides, meteors, and explosions are regularly detected on seismometers (De Angelis et al, ; Edwards et al, ; Fee et al, , ; Ichihara et al, ; Johnson & Malone, ; Langston, ; Matoza & Fee, ; Nishida & Ichihara, ; Smith et al, ; Tauzin et al, ; Walker et al, ). Here we present a method to determine the back azimuth to an acoustic source detected on a nearly collocated three‐component seismometer and infrasonic microphone.…”