Date of Award
2025
Document Type
Open Access Master's Thesis
Degree Name
Master of Science in Geology (MS)
Administrative Home Department
Department of Geological and Mining Engineering and Sciences
Advisor 1
Gregory P. Waite
Committee Member 1
Rudiger P. Escobar Wolf
Committee Member 2
Luke J. Bowman
Abstract
Pyroclastic Density Currents (PDCs) are deadly flows of ash, tephra, gas, and solidified magma which predominantly occur when an ash plume collapses during a volcanic eruption. PDCs are also able to form when large deposits of ash at the summit of a volcano are displaced during an eruption and flow downslope. This is typically the mechanism behind PDCs that occur at Volcán de Fuego such as one that occurred in 2018 killing at least 430 people. The purpose of this paper is to track the propagation of PDCs that occurred at Fuego seismologically in order to better understand how they behave and, ultimately, better protect people in the future. The PDCs studied here occurred during eruptions on July 4 and December 11, 2022, and were recorded with four to seven seismic stations depending on the event. Three of these stations are within 100 m of the channels down which the PDCs flowed, much closer than is typical for an attempt to track PDCs.
Three methods were used to track the PDCs while one other was used to determine their velocities. The methods for tracking are referred to as the Envelope, RMS, and Linearized Decay methods while the method used to find velocity is referred to as the Cross Correlation method. The Cross Correlation method relies on calculating the cross correlation of seismic envelopes between two seismometers located close to the PDC’s path. This returns a time delay which, when divided by the distance between the seismometers, results in a velocity measurement for each event. While this method failed to produce results for the July 4 event due to anthropogenic interference, velocities for the December event are found to be between 9.9 and 13.5 m/s.
The Envelope, RMS, and Linearized Decay methods all rely on equations for amplitude decay. The first two methods used an equation that was dependent on anelastic attenuation factors. These methods are nearly identical, the only difference being that one analyzes the envelope of the seismogram, while the other uses the seismogram as is. Both methods produced similar results which displayed the location of the PDC far from the stations that recorded the highest amplitudes. This is unexpected as the point behind using equations for amplitude decay is to find the location where the amplitude is highest at any given point in time. This location is then presumed to be the source as amplitude decreases with distance from the source. The reason this failed is likely a result of the equation requiring attenuation values that are not well understood when close to the source location. The third tracking method, referred to as the Linearized Decay method, worked well as the equation did not require these values. This method placed the PDC at the expected locations, in expected times, and estimated the velocity of the PDC to be around 7 m/s for the December event. Both this velocity, and the velocities found by the cross correlation are slow compared to the average PDC but that is likely due to a low topographic slope and the fact that these PDCs are relatively small.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Krier, Jacob A., "PROXIMAL SEISMIC TRACKING OF PYROCLASTIC DENSITY CURRENTS AT VOLCÁN DE FUEGO, GUATEMALA", Open Access Master's Thesis, Michigan Technological University, 2025.