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.