On the origin of the signals observed across the seismic spectrum

Díaz, Jordi

doi:10.1016/j.earscirev.2016.07.006

Cited by 32 publications

(35 citation statements)

References 55 publications

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“…It has been widely documented that the seismic signal has different sources and generation mechanisms at different frequency bands 1 , 12 . One of the best tools to illustrate those differences are the spectrograms, a representation in which the seismic acceleration is decomposed to get the evolution of its power spectral density in function of time and frequency, expressed in dB and relative to a reference value of 1 (m 2 /s 4 )/Hz (Fig.…”

Section: An Overview Of the Seismic Spectramentioning

confidence: 99%

Urban Seismology: on the origin of earth vibrations within a city

Díaz

Ruiz

Sánchez‐Pastor

et al. 2017

Sci Rep

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105

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Urban seismology has become an active research field in the recent years, both with seismological objectives, as obtaining better microzonation maps in highly populated areas, and with engineering objectives, as the monitoring of traffic or the surveying of historical buildings. We analyze here the seismic records obtained by a broad-band seismic station installed in the ICTJA-CSIC institute, located near the center of Barcelona city. Although this station was installed to introduce visitors to earth science during science fairs and other dissemination events, the analysis of the data has allowed to infer results of interest for the scientific community. The main results include the evidence that urban seismometers can be used as a easy-to-use, robust monitoring tool for road traffic and subway activity inside the city. Seismic signals generated by different cultural activities, including rock concerts, fireworks or football games, can be detected and discriminated from its seismic properties. Beside the interest to understand the propagation of seismic waves generated by those rather particular sources, those earth shaking records provide a powerful tool to gain visibility in the mass media and hence have the opportunity to present earth sciences to a wider audience.

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Section: An Overview Of the Seismic Spectramentioning

confidence: 99%

Urban Seismology: on the origin of earth vibrations within a city

Díaz

Ruiz

Sánchez‐Pastor

et al. 2017

Sci Rep

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105

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“…The panoply of transient physical processes at active volcanoes radiate a remarkable variety of elastic wave signal types (e.g., Chouet & Matoza, ; Gasparini et al, ) that span the full frequency/period range of broadband seismology (from hundreds of hertz to thousands of seconds) (e.g., Diaz, ). These source processes encompass subareal or contained gas‐driven explosions (e.g., Hidayat et al, ), stick‐slip faulting (e.g., Kendrick et al, ), tractions arising from turbulent (including eruption column) fluid flow (e.g., Matoza et al, ), diverse types of elastic resonance (e.g., O'Brien & Bean, ), reaction forces arising from fluid (e.g., Aster et al, ; James et al, ; Nishimura et al, ) and/or gas (e.g., D'Auria & Martini, ; Prejean & Brodsky, ) transport, pressurization, and volumetric injection or withdrawal (e.g., Lough et al, ; Prejean et al, ).…”

Section: Introductionmentioning

confidence: 99%

Multiyear Shallow Conduit Changes Observed With Lava Lake Eruption Seismograms at Erebus Volcano, Antarctica

et al. 2018

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We analyze near‐repeating broadband seismograms from nearly 3,000 eruptions (2003–2011) from the Erebus volcano lava lake to investigate temporal changes in the shallow eruptive dynamics of an open conduit volcano. Cross‐correlation analysis reveals progressive variable time lags between correlation‐aligned short period (SP) and very long period (VLP) seismogram components ranging over approximately ±1 s and evolving over weeks to months. Lava lake eruptions both excite an SP explosion seismic signal and gravitationally unload the conduit. After a delay of several seconds, this unloading excites a posteruptive, minute‐long VLP seismic signal that persist for several minutes until the lava lake is refilled. VLP‐SP lag variations are consistent across multiple seismic stations and are independent of eruption size, spectral characteristics, eruption frequency, and lava lake morphology changes. Lag changes are interpreted in terms of variable communication time between eruptions and the subsequent elastic and gravitational response of a tomographically imaged near‐summit magma storage and VLP source region several hundred meters below the lava lake. Tomographic and VLP moment tensor studies, combined with modeling, suggest that the elastodynamic communication time between the distinct SP and VLP source regions is mediated by conduit‐guided Stoneley waves within the uppermost magma‐filled conduit system that are sensitive to small shallow conduit geometry changes. Conduit geometry changes may be driven by internal or external processes, including conduit wall melting and refreezing, repeated eruptive slug erosion, and deformation from inner crater inflation or collapse.

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“…The time variation pattern in seismic and electric data is very similar between 0.1 and 0.01 Hz. The electric field data are dominated by signals related to subway activity till frequencies above 1 Hz, while the seismic data above 0.1 Hz reflect the well-known variations related to the oceanic wave activity (i.e., Díaz 2016). Note that the large peak observed the 22nd October in the seismic data corresponds to the arrival of the seismic waves from a series of three earthquakes near Vancouver (Canada), with magnitudes 6.5, 6.8 and 6.5 and origin times 05:39, 06:16and 06:22 UTC.…”

Section: Collocated Electric Field Measurementsmentioning

confidence: 96%

“…This procedure, common in seismological practice, removes the effect of the recording instrument, allowing measuring the effective movement of the soil. Data processing is very simple, as it only includes the application of a low-pass filter with a corner frequency of 0.01 Hz to suppress the high-frequency signals related to oceanic waves and human activities (e.g., Díaz 2016). We identify a detection when a long period pulse is observed at the time of the reported SSC, clearly outstanding the previous minutes of the filtered signal.…”

Section: Ssc Observations On Global Seismic Networkmentioning

confidence: 99%

On the observation of magnetic events on broad-band seismometers

Díaz¹,

Ruiz²,

Curto³

et al. 2020

Earth Planets Space

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The objective of this contribution is to get new insights into the effects of magnetic field variations of natural and anthropogenic origin on broad-band seismic stations. Regarding natural sources of magnetic perturbations, we have investigated if the Sudden Storm Commencements (SSC) cataloged during the 24th solar cycle (2008-2019) can be systematically identified in broad-band seismic stations distributed worldwide. The results show that the 23 SSC events with a mean amplitude above 30 nT and most of those with lower energy but still clearly identified in the magnetometer detection network can be observed at broad-band stations' network using a simple low-pass filter. Although the preliminary impulse of those signals is usually stronger at stations located at high latitudes, major SSC are observed at seismic stations distributed worldwide. Regarding anthropogenic sources, we focus on the short period seismic signals recorded in urban environments which are correlated with the activity of the railway transportation system. We have analyzed collocated measurements of electric field and seismic signals within Barcelona, evidencing that significant changes in the electric field following the activity of the transportation systems can be attributed to leakage currents transmitted to the soil by trains. During space weather events, electric currents in the magnetosphere and ionosphere experience large variations inducing telluric currents near the Earth surface, which in turn generate a secondary magnetic field. In the case of underground trains, leakage currents are transmitted to the soil, which in turn can result in local variations in the magnetic field. The observed signals in modern seismometers can be related to the reaction of the suspension springs to these magnetic field variations or to the effect of the magnetic field variations on the force transducers used to keep the mass fixed.

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On the origin of the signals observed across the seismic spectrum

Cited by 32 publications

References 55 publications

Urban Seismology: on the origin of earth vibrations within a city

Urban Seismology: on the origin of earth vibrations within a city

Multiyear Shallow Conduit Changes Observed With Lava Lake Eruption Seismograms at Erebus Volcano, Antarctica

On the observation of magnetic events on broad-band seismometers

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