Testing Small-Aperture Array Analysis on Well-Located Earthquakes, and Application to the Location of Deep Tremor

2008 ◽  
Vol 98 (2) ◽  
pp. 620-635 ◽  
Author(s):  
M. La Rocca ◽  
D. Galluzzo ◽  
S. Malone ◽  
W. McCausland ◽  
G. Saccorotti ◽  
...  
Keyword(s):  
Array Analysis ◽  
Small Aperture ◽  
Aperture Array

Detection and source parameterization of small-energy fireball events in Western Alps with ground-based infrasonic arrays

2021 ◽  
Author(s):  
Giacomo Belli ◽  
Emanuele Pace ◽  
Emanuele Marchetti
Keyword(s):  
Western Alps ◽  
Apparent Velocity ◽  
Array Analysis ◽  
Small Energy ◽  
Small Aperture ◽  
Energy Estimation ◽  
Trajectory Reconstruction ◽  
Tnt Equivalent ◽  
Back Azimuth ◽  
Aperture Arrays

Summary We present infrasound signals generated by four fireball events occurred in Western Alps between 2016 and 2019 and that were recorded by small aperture arrays at source-to receiver distances < 300 km. Signals consist in a series of short-lived infrasonic arrivals that are closely spaced in time. Each arrival is identified as a cluster of detections with constant wave parameters (back-azimuth and apparent velocity), that change however from cluster to cluster. These arrivals are likely generated by multiple infrasonic sources (fragmentations or hypersonic flow) along the entry trajectory. We developed a method, based on 2D ray-tracing and on the independent optically determined time of the event, to locate the source position of the multiple arrivals from a single infrasonic array data and to reconstruct the 3D trajectory of a meteoroid in the Earth's atmosphere. The trajectories derived from infrasound array analysis are in excellent agreement with trajectories reconstructed from eyewitnesses reports for the four fireballs. Results suggest that the trajectory reconstruction is possible for meteoroid entries located up to ∼300 km from the array, with an accuracy that depends on the source-to-receiver distance and on the signal-to-noise level. We also estimate the energy of the four fireballs using three different empirical laws, based both on period and amplitude of recorded infrasonic signals, and discuss their applicability for the energy estimation of small energy fireball events ($\le 1{\rm{kt\,\,TNT\,\,equivalent}}$).

scholarly journals Lg-coda Q in the central part of the East European platform from small aperture array “Mikhnevo” data

2019 ◽  
Vol 1 (1) ◽  
pp. 57-66
Keyword(s):  
East European Platform ◽  
Seismic Attenuation ◽  
Tectonic Activity ◽  
Q Factor ◽  
Coda Q ◽  
Small Aperture ◽  
East European ◽  
Short Period ◽  
Lg Coda ◽  
Aperture Array

Whereas the quality factor Q is one of the basic parameters required in seismic hazard estimation, no systematic studies of seismic attenuation factors have been carried out in the central part of the East European Platform due to the lack of a dense seismic network and a small number of regional earthquakes. The main part of the events, recorded by the small aperture array “Mikhnevo” 80 km to the south of Moscow, consists of industrial explosions of different magnitude. The idea of the paper is to apply conventional seismic methods to the analysis of seismic waveforms of industrial explosions. The paper focuses on the Lg coda of the quarry blast in “Mikhailovsky” quarry 300 km from the array. Vertical components of the short-period and broad band records of the sensors positioned in the well at the depth 20 m are processed according to the SSR algorithm, suggested by Xie and Nuttli, 1988, and extensively used by Mitchell et al in different regions of the world. The advantages of the method imply exclusion of the source and site characteristics by taking spectral ratios of the successive time windows of the coda. Compared to the earthquake waveforms, the Lg coda of explosions is shorter, less regular and contains higher frequencies. The length of coda varies according to the noise level. We selected 14 events from the same quarry in different years, which demonstrate remarkable stability of the waveforms. All the events were processed individually to obtain the frequency dependence of Q in the form Q(f)=Q0 f , where Q0 is the Q factor at the frequency 1 Hz and  is the power. To produce stable estimates of Q0 and  individual values were averaged for frequency bands: 2-6 Hz, 2-7 Hz, 3-6 Hz, 3-7 Hz for different length of coda. The preferable frequency range for Lg coda Q studies of quarry blasts is suggested as 3-6 Hz, which avoids instability of coda in 1-3 Hz interval, presumably caused by local site effect, connected with the 3 km thick sedimentary layer. The Q estimate of Q0=584±89, =0.41±0.06 proves considerable heterogeneity of the upper crust in the region. Speaking about Q factor as an indicator of the tectonic activity, the studied area can be related to a region of moderate activity.

scholarly journals Small-aperture array as a tool to monitor fluid injection- and extraction-induced microseismicity: applications and recommendations

2018 ◽  
Vol 67 (1) ◽  
pp. 311-326 ◽  
Author(s):  
Nasim Karamzadeh ◽  
Daniela Kühn ◽  
Marius Kriegerowski ◽  
José Ángel López-Comino ◽  
Simone Cesca ◽  
...  
Keyword(s):  
Fluid Injection ◽  
Small Aperture ◽  
Aperture Array
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