Real-time assessment of potential seismic migration within a monitoring network using Red-flag SARA

Tan, Chiou Ting; Taisne, Benoît; Neuberg, Jürgen; Basuki, Ahmad

doi:10.1016/j.jvolgeores.2019.07.004

Cited by 9 publications

(7 citation statements)

References 25 publications

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“…In other words, positive residuals indicate more heterogeneous and/or less attenuative bodies and negative residuals less heterogeneous and/or more attenuative bodies. Indeed, we noted correlations between our residual maps and 3D V p tomographic images from previous studies at these volcanoes (Nishi, 2002;Tanaka, Hamaguchi, Nishimura, et al, 2002;Tomatsu et al, 2001;Yamawaki et al, 2004). Comparison of our map at Kirishima (Figure 11a) and the P wave velocity image of Tomatsu et al (2001) at depths between −1.5 and −0.5 km below sea level (Figures 10a and 10b of Tomatsu et al, 2001) indicates that the areas of positive residuals observed near shot locations S1 and S5 (Figure 2a) and the summit of Shimoe-dake correspond to low velocities of around V p = 2 km/s.…”

Section: 1029/2020jb020249supporting

confidence: 71%

“…Despite such systematic differences, our results clearly show that a thin, surficial, heterogeneous layer underlain by less heterogenous layers is a common feature. As discussed by Kumagai et al (2018), this surface layer may correspond to low-velocity surface layers commonly observed in tomographic images (e.g., Aoki et al, 2009;Molina et al, 2005;Nishi, 2002;Tanaka, Hamaguchi, Nishimura, et al, 2002;Tomatsu et al, 2001;Yamawaki et al, 2004;Zollo et al, 2003) and low-resistivity surface layers inferred from electromagnetic surveys at various volcanoes (e.g., Aizawa et al, 2008;Alanis et al, 2013;Kanda et al, 2008;Nurhasan et al, 2006;Yamaya et al, 2013). This layer may consist of unconsolidated and/or highly fractured materials, hydrothermal fluids, and altered clay minerals, all of which are common to volcanic edifices and produce strongly scattering wavefields.…”

Section: Discussionmentioning

confidence: 83%

“…For our analyses at these volcanoes, we used active sources produced by dynamite blasts at Kirishima in 1994 (Kagiyama et al, 1995;Tomatsu et al, 1997Tomatsu et al, , 2001Tsutsui et al, 1996), Unzen in 1995 (Matsushima et al, 1997;Nishi, 2002), Bandai in 1997 (Yamawaki et al, 2004), and Iwate in 2000 (Tanaka, Hamaguchi, Yamawaki et al, 2002;Tanaka, Hamaguchi, Nishimura, et al, 2002) (Figure 2). These seismic explorations were conducted by the Japanese national project to better understand volcano structures (Kagiyama et al, 1995).…”

Section: Active Sources At Kirishima Unzen Bandai and Iwatementioning

confidence: 99%

“…These seismic explorations were conducted by the Japanese national project to better understand volcano structures (Kagiyama et al, 1995). More than 100 short-period seismometers with local data loggers were temporarily deployed to observe earthquakes excited by chemical explosions at each volcano ( Figure 2), and their detailed V p structures were estimated (Nishi, 2002;Tanaka, Hamaguchi, Nishimura, et al, 2002;Tomatsu et al, 1997Tomatsu et al, , 2001Tsutsui et al, 1996;Yamawaki et al, 2004). In our analyses of the envelope widths of active sources at these volcanoes, we excluded some explosions located far from the volcanic centers, and some stations very close to sea level because they may not provide accurate structural information.…”

Section: Active Sources At Kirishima Unzen Bandai and Iwatementioning

confidence: 99%

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Scattering and Attenuation Characteristics at Volcanoes Inferred From Envelope Widths of Natural and Active Seismic Sources

2020

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Seismic scattering and attenuation at volcanoes, thought to be strongest on the Earth, can be used to map volcanic feeding systems. We systematically analyzed high-frequency (5-10 Hz) seismograms of volcano-tectonic earthquakes at Galeras volcano (Colombia) and active sources at Kirishima, Unzen, Bandai, and Iwate volcanoes (Japan) to investigate their scattering and attenuation characteristics. The envelope widths estimated from these seismograms were compared with those calculated by Monte Carlo envelope simulations for 1D layered models parameterized by the scattering mean free path and the quality factor of medium attenuation for S waves. Our results indicated a surficial, highly heterogeneous, and attenuative layer up to around 1 km thickness at all studied volcanoes. The strongest heterogeneities at volcanoes thus exist in a thin surface layer, likely comprising unconsolidated and/or highly fractured materials. Using the space-weighting function for diffusive wavefields, we mapped the residuals between observed envelope widths and those calculated with our estimated 1D models at Kirishima, Unzen, Bandai, and Iwate. These maps showed spatial distributions of the envelope-width residuals were unique to each volcano and correlated with P wave velocity tomographic images. Areas of positive residuals correspond to low-velocity anomalies and thus to heterogeneous, strongly scattering rocks, whereas areas of negative residuals correspond to high-velocity anomalies and thus less heterogeneous volcanic or basement rocks. Our results demonstrate that envelope widths can improve the characterization of scattering and attenuation structures beneath volcanoes.

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Section: 1029/2020jb020249supporting

confidence: 71%

Section: Discussionmentioning

confidence: 83%

Section: Active Sources At Kirishima Unzen Bandai and Iwatementioning

confidence: 99%

Section: Active Sources At Kirishima Unzen Bandai and Iwatementioning

confidence: 99%

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Scattering and Attenuation Characteristics at Volcanoes Inferred From Envelope Widths of Natural and Active Seismic Sources

2020

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“…The amplitude source location (ASL) method proposed by Yamasato () and Battaglia and Aki () and the seismic amplitude ratio method of Taisne et al () have enabled the locations of LP and VLP events and tremor with emergent onsets to be determined. These methods use high‐frequency seismic amplitudes and assume isotropic radiation of S waves and have been widely applied to volcanoseismic signals at various volcanoes (Battaglia, ; Battaglia, Aki, & Ferrazzini, ; Battaglia, Aki, & Staudacher, ; Caudron et al, ; Caudron, Taisne, et al, ; Caudron, White, et al, ; Ichihara & Matsumoto, ; Ichimura et al, ; Jolly et al, ; Kumagai et al, ; Kumagai et al, ; Kumagai, Palacios, et al, ; Kumagai et al, ; Kumagai et al, ; Kumagai et al, ; Kurokawa et al, ; Maeda et al, ; Ogiso et al, ; Ogiso & Yomogida, , ; Tan et al, ; Walsh et al, ; Walter et al, ). These methods have also been used to detect moving sources of tremor signals associated with eruptions (Ichihara & Matsumoto, ; Kumagai, Palacios, et al, ; Ogiso & Yomogida, ), magmatic intrusions (Caudron et al, 2018b; Taisne et al, ), and lahars (Ogiso & Yomogida, ).…”

Section: Introductionmentioning

confidence: 99%

Amplitude Source Location Method With Depth‐Dependent Scattering and Attenuation Structures: Application at Nevado del Ruiz Volcano, Colombia

et al. 2019

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The amplitude source location (ASL) method, which uses high-frequency amplitudes based on the assumption of isotropic radiation of S waves, was tested with envelope waveforms simulated from depth-dependent scattering and attenuation structures at Nevado del Ruiz volcano, Colombia. Our test results indicate that estimated ASLs are more accurate when a two-layer attenuation model is used than when a homogenous attenuation model is used, as has commonly been done in previous studies. We applied the ASL method with a two-layer attenuation model to the high-frequency (5-10 Hz) band of volcanotectonic (VT) earthquakes, long-period (LP) and very long period (VLP) events, and tremor recorded in 2016 at Nevado del Ruiz. Results indicate that the differences between ASLs and VT earthquake hypocenters (determined using onset arrival times) were smaller for a two-layer model compared to a homogeneous model. Our determined ASLs for LP and VLP events and tremor were distributed along a NW-dipping plane beneath the summit crater, near and above a region with high P to S wave velocity ratios that has been interpreted as shallow magma storage. This plane may represent weak zones along the Palestina fault system. Our results suggest that LP and VLP events and tremor occur during magma ascent along the fault system. This study demonstrates that the ASL method with a depth-dependent attenuation model is useful to improve the accuracy of estimated source locations for volcanoseismic signals.

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Detecting sources of shallow tremor at neighboring volcanoes in the Virunga Volcanic Province using seismic amplitude ratio analysis (SARA)

et al. 2023

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Volcano monitoring requires simple techniques to rapidly identify the cause of volcanic unrest. The so-called RSAM (real-time seismic amplitude measurements) technique, used in many observatories, is a good example of extracting information from seismograms with minimal processing. Built on a similar principle, the more recent seismic amplitude ratio analysis (SARA) technique allows locating migrating seismicity at high frequency (> 2 Hz, e.g., due to dike intrusions) under certain assumptions. However, such analysis generally requires a dense distribution of stations close to the seismic sources (depending on the magnitude) and/or station sites undisturbed by human activity. In a more straightforward and qualitative approach, computing amplitude ratios between station pairs can also allow for the detection of temporal and (2D) spatial changes of volcanic activity. In this work, we adopt such a simplified approach of SARA in order to characterize seismic tremors originating from two open-vent neighboring volcanoes, Nyiragongo and Nyamulagira, in the Virunga Volcanic Province (VVP) in the Democratic Republic of the Congo (DRC). In contrast with previous studies, we focus here on the low-frequency band (0.3-1 Hz), free from anthropogenic noise and sensitive to shallow volcanic tremors linked to intermittent or permanent intra-crater eruptive activity recorded through the large-aperture local network. We apply for the first time the SARA methodology for volcanic sources predominantly generating surface waves and propagating over long distances. The analysis is performed on more than two years of continuous seismic data. Seismic amplitude analysis in this frequency band is strongly influenced by the short-period microseisms originating from nearby Lake Kivu. Despite this diurnal to seasonal amplitude variability, SARA successfully detects continuous volcanic tremor activity and its arrest at both volcanoes. In light of these findings, we discuss the applicability of the method to the continuous, real-time detection, and characterization of long-period shallow volcanic tremor sources in this region. KeywordsVirunga • Nyiragongo • Nyamulagira • Volcanic tremors • Lake microseisms • SARA Résumé La surveillance des volcans actifs fait souvent appel à des techniques simples pour détecter les changements ou évaluer rapidement les causes d'une activité soutenue. La technique appelée RSAM (Mesure des Amplitudes Sismiques en temps Réel), fréquemment utilisée dans les observatoires volcanologiques, est un bon exemple d'extraction d'informations par analyse minimale de séismogrammes. En se basant sur un principe similaire, la récente technique d'Analyse des Rapports d'Amplitudes Sismiques (SARA) permet, sous certaines conditions, de localiser la migration de la sismicité à haute fréquences (> 2 Hz) liée, par exemple, à une intrusion magmatique. Cependant, cette méthode d'analyse nécessite une distribution dense Editorial responsibility: A. Cannata This paper constitutes part of a topical collection: Open-vent volcanoes * Josué ...

show abstract

Real-time assessment of potential seismic migration within a monitoring network using Red-flag SARA

Cited by 9 publications

References 25 publications

Scattering and Attenuation Characteristics at Volcanoes Inferred From Envelope Widths of Natural and Active Seismic Sources

Scattering and Attenuation Characteristics at Volcanoes Inferred From Envelope Widths of Natural and Active Seismic Sources

Amplitude Source Location Method With Depth‐Dependent Scattering and Attenuation Structures: Application at Nevado del Ruiz Volcano, Colombia

Detecting sources of shallow tremor at neighboring volcanoes in the Virunga Volcanic Province using seismic amplitude ratio analysis (SARA)

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