Investigation of the preparation process of seismic events with the help of seismic noise analysis

Abstract. The island of Tenerife (Canary Islands, Spain), is showing possible signs of reawakening after its last basaltic strombolian eruption, dated 1909 at Chinyero. The main concern relates to the central active volcanic complex Teide - Pico Viejo, which poses serious hazards to the properties and population of the island of Tenerife (Canary Islands, Spain), and which has erupted several times during the last 5000 years, including a subplinian phonolitic eruption (Montaña Blanca) about 2000 years ago. In this paper we show the presence of low frequency seismic noise which possibly includes tremor of volcanic origin and we investigate the feasibility of using it to forecast, via the material failure forecast method, the time of occurrence of discrete events that could be called Volcano-Tectonic or simply Tectonic (i.e. non volcanic) on the basis of their relationship to volcanic activity. In order to avoid subjectivity in the forecast procedure, an automatic program has been developed to generate forecasts, validated by Bayes theorem. A parameter called "forecast gain" measures (and for the first time quantitatively) what is gained in probabilistic terms by applying the (automatic) failure forecast method. The clear correlation between the obtained forecasts and the occurrence of (Volcano-)Tectonic seismic events - a clear indication of a relationship between the continuous seismic noise and the discrete seismic events - is the explanation for the high value of this "forecast gain" in both 2004 and 2005 and an indication that the events are Volcano-Tectonic rather than purely Tectonic.

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Surface wave dispersion measurements from ambient seismic noise analysis in Italy

Geophysical Journal International ◽

10.1111/j.1365-246x.2009.04476.x ◽

2010 ◽

Vol 180 (3) ◽

pp. 1242-1252 ◽

Cited By ~ 41

Author(s):

Hongyi Li ◽

Fabrizio Bernardi ◽

Alberto Michelini

Keyword(s):

Surface Wave ◽

Seismic Noise ◽

Noise Analysis ◽

Wave Dispersion ◽

Ambient Seismic Noise ◽

Surface Wave Dispersion

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Ambient Seismic Noise Analysis Associated with the 2010 Eruption of Merapi Volcano Using Temporal Variations of Randomness and Background Noise

International Journal of Geophysics ◽

10.1155/2020/8853376 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Afif Rakhman ◽

Wahyudi ◽

Agus Budi Santoso ◽

Hanik Humaida ◽

Wiwit Suryanto

Keyword(s):

Background Noise ◽

Seismic Noise ◽

Noise Analysis ◽

Temporal Variations ◽

Permutation Entropy ◽

Merapi Volcano ◽

Frequency Bands ◽

Volcano Eruption ◽

Power Spectral ◽

Short Period

We present the combination of permutation entropy (PE) and power spectral density (PSD) analysis on continuous seismic data recorded by short-period seismic stations during the 2010 Merapi volcano eruption. The calculation of PE aims at characterizing the randomness level in seismic noise, while the PSD parameters use to detect the background noise level in various frequency bands. It was previously observed that a significant reduction of randomness before the volcano eruption could be indicated as one of the short-term precursors due to the lack of high frequencies (>1 Hz) in the noise wave-field caused by high absorption losses as the hot magma uprises to the upper crust. The results show no significant reduction in signal randomness before the eruption series. The characteristic of events during the preeruptive period and the crisis tends to be chaotic (PE in the range 0.9 to 1). Further calculations show that the standard deviation in PE decreased in four days before the first eruption onset on 26 October. PE was stable at the highest values (very close to 1) and gradually returned to the previous fluctuation after the eruption onset. The level of background noise in the low- and high-frequency bands appeared to have the same tendency. The two main eruptions correspond to the two highest peaks of noise levels.

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WIDE‐BAND VELOCITY FILTERING—THE PIE‐SLICE PROCESS

Geophysics ◽

10.1190/1.1439310 ◽

1963 ◽

Vol 28 (6) ◽

pp. 948-974 ◽

Cited By ~ 115

Author(s):

Peter Embree ◽

John P. Burg ◽

Milo M. Backus

Keyword(s):

Seismic Noise ◽

Simple Wave ◽

Wide Band ◽

Wave Number ◽

Seismic Events ◽

Multiple Attenuation ◽

Noise Data ◽

A New Technique ◽

Velocity Filtering ◽

Record Section

A new technique has been developed which makes it possible to process a seismic record‐section in such a way that all seismic events with dips in a given range are preserved with no alteration over a wide frequency band, while all seismic events with dips outside the specified range are uniformly and severely attenuated. By applying this process to a noisy record‐section, a record‐section may be obtained which has all events within a specified dip range perfectly preserved, and very high‐velocity noise essentially eliminated, a result which is impossible by simple wave‐number filtering or conventional array usage. In structurally complex areas where several steeply dipping events interfere, the technique may be applied to separate the events with different dips. In areas where a normal‐moveout contrast exists between primaries and multiples, the technique may be used for wide‐band multiple attenuation. By application of a “rotating Pie‐Slice” to micro‐spread noise data, seismic noise may be separated on the basis of propagation velocity, and a clearer picture of the seismic noise problem obtained. The “rotating Pie‐Slice” also provides a means of uncovering diffractions and other steeply‐curved events from a record section. The paper discusses the motivation and implementation of the process and its application to both synthetic and actual data.

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Investigating Spatio-temporal Changes in Subglacial Hydrology from Dense Array Seismology.

10.5194/egusphere-egu2020-10710 ◽

2020 ◽

Author(s):

Ugo Nanni ◽

Florent Gimbert ◽

Philippe Roux ◽

Albanne Lecointre

Keyword(s):

Water Flow ◽

Seismic Noise ◽

Water Pressure ◽

Noise Analysis ◽

Drainage System ◽

Dense Array ◽

Noise Sources ◽

Spatio Temporal ◽

Surrounding Areas ◽

Subglacial Drainage

Subglacial hydrology strongly modulates glacier basal sliding, and thus likely exerts a major control on ice loss and sea-level rise. However, the limited direct and spatialized observations of the subglacial drainage system make difficult to assess the physical processes involved in its development. Recent work shows that detectable seismic noise is generated by subglacial water flow, such that seismic noise analysis may be used to retrieve the physical properties of subglacial channelized water flow. Yet, investigating the spatial organisation of the drainage system (e.g. channels numbers and positions) together with its evolving properties (e.g. pressure conditions) through seismic observations remains to be done. The objective of this study is to bring new insights on the subglacial hydrology spatio-temporal dynamics using dense array seismic observations.We use 1-month long ground motion records at a hundred of sensors deployed on the Argenti&#232;re Glacier (French Alps) during the onset of the melt season, when the subglacial drainage system is expected to strongly evolve in response to the rapidly increasing water input. We conduct a multi-method approach based on the analysis of both amplitude and phase maps of seismic signals. We observe characteristic spatial patterns, consistent across those independent approaches, which we attribute to the underlying subglacial drainage system.The phase-driven approach shows seismic noise sources that focuses in the along-flow direction as the water input increases. We identify this evolution as the development of the main subglacial channel whose position is coherent with the one expected from hydraulic potential calculations. During periods of rapid changes in water input (5 days over 31) and concomitant glacier acceleration the amplitude-driven approach shows spatial pattern highly consistent with the seismic noise sources location. At this time, we suggest that the spatial variations in the amplitude are representative of the water pressure conditions in subglacial channels and surrounding areas. Our spatialized observations therefore reveal the spatio-temporal evolution of the subglacial drainage system together with its changing pressure conditions. We observe, for instance, that channels develop at the very onset of the melt-season and rapidly capture the water from surrounding areas. Such unique observations may allow to better constrain the physics of subglacial water flow and therefore strengthen our knowledge on the dynamics of subglacial environments.

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Problems of operative prediction of seismic events. The suggested way to solution

Вестник КРАУНЦ. Физико-математические науки ◽

10.26117/2079-6641-2021-35-2-120-132 ◽

2021 ◽

pp. 120-132

Author(s):

В.А. Паровышный ◽

Л.М. Богомолов ◽

Ю.В. Сохатюк ◽

Д.В. Паровышный

Keyword(s):

Experimental Studies ◽

Seismic Events ◽

Preparation Process ◽

Geophysical Fields ◽

Zone Of Influence

Рассматриваются результаты экспериментальных исследований, направленных на изучение характера временных изменений естественных геофизических полей (ЕГП) над залежью газа, расположенной в зоне влияния активного регионального разлома, а также выявление связи этих изменений с сейсмичностью. В результате эксперимента установлено, что процесс подготовки сейсмических событий сопровождается резким нарушением стабильности ЕГП над продуктивными блоками залежи. The results of experimental studies aimed at studying the nature of the temporary changes in natural geophysical fields (NGF) above the gas deposit located in the zone of influence of the active regional fault, as well as revealing the connection of these changes with seismicity are found. The experiment established that the seismic events preparation process is accompanied by a sharp instability NGF above productive reservoirs of the deposit.

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Structure of the Suasselkä postglacial fault in northern Finland obtained by analysis of local events and ambient seismic noise

Solid Earth ◽

10.5194/se-8-531-2017 ◽

2017 ◽

Vol 8 (2) ◽

pp. 531-544 ◽

Cited By ~ 1

Author(s):

Nikita Afonin ◽

Elena Kozlovskaya ◽

Ilmo Kukkonen ◽

Keyword(s):

Seismic Noise ◽

Ambient Seismic Noise ◽

Seismic Events ◽

S Wave ◽

Noise Sources ◽

Surface Wave Dispersion ◽

Velocity Models ◽

Wave Velocities ◽

Short Period ◽

Single Station

Abstract. Understanding the inner structure of seismogenic faults and their ability to reactivate is particularly important in investigating the continental intraplate seismicity regime. In our study we address this problem using analysis of local seismic events and ambient seismic noise recorded by the temporary DAFNE array in the northern Fennoscandian Shield. The main purpose of the DAFNE/FINLAND passive seismic array experiment was to characterize the present-day seismicity of the Suasselkä postglacial fault (SPGF), which was proposed as one potential target for the DAFNE (Drilling Active Faults in Northern Europe) project. The DAFNE/FINLAND array comprised an area of about 20 to 100 km and consisted of eight short-period and four broadband three-component autonomous seismic stations installed in the close vicinity of the fault area. The array recorded continuous seismic data during September 2011–May 2013. Recordings of the array have being analysed in order to identify and locate natural earthquakes from the fault area and to discriminate them from the blasts in the Kittilä gold mine. As a result, we found a number of natural seismic events originating from the fault area, which proves that the fault is still seismically active. In order to study the inner structure of the SPGF we use cross-correlation of ambient seismic noise recorded by the array. Analysis of azimuthal distribution of noise sources demonstrated that during the time interval under consideration the distribution of noise sources is close to the uniform one. The continuous data were processed in several steps including single-station data analysis, instrument response removal and time-domain stacking. The data were used to estimate empirical Green's functions between pairs of stations in the frequency band of 0.1–1 Hz and to calculate corresponding surface wave dispersion curves. The S-wave velocity models were obtained as a result of dispersion curve inversion. The results suggest that the area of the SPGF corresponds to a narrow region of low S-wave velocities surrounded by rocks with high S-wave velocities. We interpret this low-velocity region as a non-healed mechanically weak fault damage zone (FDZ) formed due to the last major earthquake that occurred after the last glaciation.

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