The effect of topography on the wavelet response of seismic arrays

ABSTRACT Ground motion with strong-velocity pulses can cause significant damage to buildings and structures at certain periods; hence, knowing the period and velocity amplitude of such pulses is critical for earthquake structural engineering. However, the physical factors relating the scaling of pulse periods with magnitude are poorly understood. In this study, we investigate moderate but damaging earthquakes (Mw 6–7) and characterize ground-motion pulses using the method of Shahi and Baker (2014) while considering the potential static-offset effects. We confirm that the within-event variability of the pulses is large. The identified pulses in this study are mostly from strike-slip-like earthquakes. We further perform simulations using the frequency–wavenumber algorithm to investigate the causes of the variability of the pulse periods within and between events for moderate strike-slip earthquakes. We test the effect of fault dips, and the impact of the asperity locations and sizes. The simulations reveal that the asperity properties have a high impact on the pulse periods and amplitudes at nearby stations. Our results emphasize the importance of asperity characteristics, in addition to earthquake magnitudes for the occurrence and properties of pulses produced by the forward directivity effect. We finally quantify and discuss within- and between-event variabilities of pulse properties at short distances.

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A Frequency-Domain-Based Algorithm for Detecting Microseismicity Using Dense Surface Seismic Arrays

Bulletin of the Seismological Society of America ◽

10.1785/0120210062 ◽

2021 ◽

Author(s):

Maria Mesimeri ◽

Kristine L. Pankow ◽

James Rutledge

Keyword(s):

Frequency Domain ◽

Detection Method ◽

Maximum Amplitude ◽

High Energy ◽

Aftershock Sequence ◽

Anthropogenic Activity ◽

Small Scale ◽

Seismic Events ◽

Small Magnitude ◽

Seismic Arrays

ABSTRACT We propose a new frequency-domain-based algorithm for detecting small-magnitude seismic events using dense surface seismic arrays. Our proposed method takes advantage of the high energy carried by S waves, and approximate known source locations, which are used to rotate the horizontal components to obtain the maximum amplitude. By surrounding the known source area with surface geophones, we achieve a favorable geometry for locating the detected seismic events with the backprojection method. To test our new detection method, we used a dense circular array, consisting of 151 5 Hz three-component geophones, over a 5 km aperture that was in operation at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) in southcentral Utah. We apply the new detection method during a small-scale test injection phase at FORGE, and during an aftershock sequence of an Mw 4.1 earthquake located ∼30 km north of the geophone array, within the Black Rock volcanic field. We are able to detect and locate microseismic events (Mw<0) during injections, despite the high level of anthropogenic activity, and several aftershocks that are missing from the regional catalog. By comparing our method with known algorithms that operate both in the time and frequency domain, we show that our proposed method performs better in the case of the FORGE injection monitoring, and equally well for the off-array aftershock sequence. Our new method has the potential to improve microseismic event detections even in extremely noisy environments, and the proposed location scheme serves as a direct discriminant between true and false detections.

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A new method of microtremor exploration using miniature seismic arrays: quick estimation of average shear velocities of the shallow soil

BUTSURI-TANSA(Geophysical Exploration) ◽

10.3124/segj.61.457 ◽

2008 ◽

Vol 61 (6) ◽

pp. 457-468 ◽

Cited By ~ 7

Author(s):

Ikuo Cho ◽

Taku Tada ◽

Yuzo Shinozaki

Keyword(s):

New Method ◽

Seismic Arrays ◽

Shallow Soil ◽

Average Shear

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Integration of onshore and offshore seismic arrays to study the seismicity of the Calabrian Region: a two steps automatic procedure for the identification of the best stations geometry

Advances in Geosciences ◽

10.5194/adgeo-36-69-2014 ◽

2014 ◽

Vol 36 ◽

pp. 69-75 ◽

Cited By ~ 1

Author(s):

A. D'Alessandro ◽

I. Guerra ◽

G. D'Anna ◽

A. Gervasi ◽

P. Harabaglia ◽

...

Keyword(s):

Numerical Simulation ◽

Network Optimization ◽

A Priori ◽

Second Step ◽

Ocean Bottom ◽

Broadband Seismometer ◽

Seismic Stations ◽

Seismic Arrays ◽

Monitoring Campaign ◽

Seismographic Network

Abstract. We plan to deploy in the Taranto Gulf some Ocean Bottom broadband Seismometer with Hydrophones. Our aim is to investigate the offshore seismicity of the Sibari Gulf. The seismographic network optimization consists in the identification of the optimal sites for the installation of the offshore stations, which is a crucial factor for the success of the monitoring campaign. In this paper, we propose a two steps automatic procedure for the identification of the best stations geometry. In the first step, based on the application of a set of a priori criteria, the suitable sites to host the ocean bottom seismic stations are identified. In the second step, the network improvement is evaluated for all the possible stations geometries by means of numerical simulation. The application of this procedure allows us to identify the best stations geometry to be achieved in the monitoring campaign.

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A new approach for three component seismic array processing

Annals of Geophysics ◽

10.4401/ag-4205 ◽

1994 ◽

Vol 37 (3) ◽

Author(s):

O. K. Kedrov ◽

V. E. Permyakova

Keyword(s):

Noise Suppression ◽

Effective Means ◽

Seismic Arrays ◽

Robust Detection ◽

Detection And Identification ◽

Seismic Vibrations ◽

Band Pass ◽

Polarization Filtering ◽

Detection Of Signals ◽

New Procedures

The new concept and methodology of regional seismic arrays (RSA) equipped by three component (3 C) sensors (Z, NS, EH9, are proposed. Such system could be more perfect tool of Earth interior investigations. This aim can be achieved by introduction of polarization filtering of 3 C seismic vibrations as an effective means of noise suppression and robust detection and identification of secondary body phases of the signals. The proposed algorithm is based on: 1) linear phase band pass frequency filtering of N 3 C records in M bands; 2) polarization filtering of all 3 C records in all L directions where array beams are routinely oriented; 3) calculation of L beams in M bands using polarized P, SV and SH traces of individual sensors; 4) detection of signals on the L*M P, SV and SH traces; 5) location of the event. The main new procedures are 2) and 3). Due to these new approaches the procedures 4) and 5) will be improved in comparison with,those routinely used today at RSA's. This work includes the theoretical consideration of proposed method efficiency and preliminary experimental results.

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