investigative seismology in cheverly, maryland · ingate, s. f., husebye, e. s., &...
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Investigative Seismology in Cheverly, MarylandResolution of “Boom” Events with Perspectives on Seismic Signatures of Cultural Noise
Pete Meehan – Senior Thesis I
With the Advising of: Vedran Lekic Ph.D.
Loud “boom” events have disturbed residents of Cheverly,Maryland for the past decade. Town officials requested theassistance of the UMD Seismology Laboratory in locating the sourceof Booms. This project seeks to resolve the source of the “booms”by applying methods of array seismology.
“Booms” are the audible manifestation of P-wave arrival fromshallow, low magnitude earthquakes.
Hypothesis
Introduction
MethodsHypothesis will be tested with the collection of continuous, threecomponent, seismic data by a nodal array of twenty-two ZLand 3C,three component seismometers.
Results
Acknowledgements and References
Figure 3: Kamchatka 6.6 Earthquake – March 29th, 2017Wave arrival times with displacement (Left), adapted from IRIS. Seismogram recorded by Cheverly arrayshowing P-wave arrival at 12:20:30 am. (Right)
Figure 2: April 2nd “Boom” - Seismogram
Arrival of wave at 2:17:02 am (1020 s) is consistentwith residential report of boom at 2:17 am.
Coherent Wave form seen across all sevenseismometers of the sample sub-array.
Signal exhibited maximum spectral power at 7 Hz,under sixth-order, 100 Hz low pass filtering.
Signal shows differentiated arrival times at eachlocation
Figure 3: April 2nd “Boom” - PreliminarySource Location
Source location contours based on manuallypicked arrival times.
Assumed wave velocity of 343 m/s (speed ofsound in air) based on resident who reportedhearing the “boom”
Figure 4: Power Spectrum of Cheverly Cultural NoisePlot of seismogram (Top) and spectrogram (Bottom) show contrastincoherent seismogram and spectrogram with recognizable signatures.
Rost, S., and C. Thomas, Array seismology: Methods and applications, Rev. Geophys., 40(3), 1008,
doi:10.1029/2000RG000100, 2002.
Ingate, S. F., Husebye, E. S., & Christoffersson, A. (1985). Regional arrays and optimum data processing
schemes. Bulletin of the Seismological Society of America, 75(4), 1155-1177.
Matlab scripts for seismometers, spectrograms, and source location adapted from Vedran Lekic
COLLEGE OF
COMPUTER, MATHMATICAL, & NATURAL SCIENCES DEPARTMENT OF GEOLOGYSeismological Laboratory
COLLEGE OF
COMPUTER, MATHMATICAL, & NATURAL SCIENCES DEPARTMENT OF GEOLOGYSeismological Laboratory
Figure 1: Distribution of “Boom” Reports –March 21, 2017“Boom” reports from the online reporting form, color coded by descriptive loudness
Barely Audible – Deafeningly Loud
Figure 2: Seismic Nodal ArraySeismic nodal array geometry (Left) with sample nodes shown as greenmarkers. An individual instrument (Right) being deployment.
Conclusions Consistency between expected and observed P-wave arrival from
the Kamchatka 6.6 earthquake demonstrates the timing and
sensitivity of the nodal array.
Identification of a reported “boom” demonstrates the ability to detect
localized events. Measurement of wave arrival times and
polarizations demonstrate the ability to locate event sources with
modest uncertainty.
Future analysis of vibrational data from full array with automated
wave arrival time picking will enable source location with greater
precision.
The analysis of cultural noise demonstrates the feasibility of time-
frequency visualization to be utilized for the characterization of
seismic signatures of cultural noise.