Cross-Correlation Analysis of Long-Term Ambient Seismic-Noise Recordings in the Caribbean Netherlands to Monitor the Volcanoes on Saba and St. Eustatius

Reinoud Sleeman; Elske de Zeeuw-van Dalfsen

doi:10.1785/0120200011

Cross-Correlation Analysis of Long-Term Ambient Seismic-Noise Recordings in the Caribbean Netherlands to Monitor the Volcanoes on Saba and St. Eustatius

Bulletin of the Seismological Society of America ◽

10.1785/0120200011 ◽

2020 ◽

Vol 110 (5) ◽

pp. 2541-2558

Author(s):

Reinoud Sleeman ◽

Elske de Zeeuw-van Dalfsen

Keyword(s):

Seismic Velocity ◽

Sine Wave ◽

Peak Ground Velocity ◽

Data Set ◽

Ground Shaking ◽

Daily Monitoring ◽

Cross Correlation Analysis ◽

Single Station ◽

Velocity Variations ◽

Different Characteristics

ABSTRACT The continuous recordings of broadband seismometers on Saba and St. Eustatius in the Lesser Antilles provide a unique and long data set to measure temporal seismic velocity variations (dv/v) at two active but quiescent volcanoes (Mt. Scenery and The Quill). We compare results from single-station cross-component (SC) correlations with cross-station cross-component (CC) correlations and achieve the best similarities within the frequency band 1.3–2.1 Hz, with average correlations of 0.82 for Saba and 0.36 for St. Eustatius, justifying the use of SC as proxy for CC at these frequencies. Temporal dv/v variations derived from 13 yr of data show different characteristics at both islands. At St. Eustatius dv/v highly correlates (0.72) with air temperature and can be modeled by a simple sine wave with a period of 1 yr. Remaining residuals reveal cohurricane dv/v drops, thus at times of the passage of a hurricane. At Saba, subsurface velocity variations show temporal coseismic changes, up to −0.49% compared with −0.19% at St. Eustatius, and thus show a higher sensitivity to ground shaking. Our data set, although limited, shows a linear relation (correlation 0.78) between the coseismic dv/v drop and peak ground velocity at Saba around 1.3 Hz. We model the associated seismic velocity recovery with an exponential decay function and we estimate the recovery time at 2 yr. After subtracting the coseismic drop and recovery model, dv/v at Saba obtained from CC data correlates with the sine model (correlation 0.71). SC may be an appealing alternative for CC for monitoring purposes; however, the use of a small network is preferred to reduce the variance in dv/v (at St. Eustatius from 0.12% to 0.05%) and to detect dv/v variations unrelated to volcanic activity (e.g., hurricane). We continue work on the implementation of CC in the daily monitoring for Mt. Scenery and The Quill.

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Single-station seismic monitoring of permafrost on Mt. Zugspitze (Germany) over the past 15 years

10.5194/egusphere-egu21-9420 ◽

2021 ◽

Author(s):

Fabian Lindner ◽

Joachim Wassermann

Keyword(s):

Travel Time ◽

Seismic Velocity ◽

Temperature Record ◽

Lapse Time ◽

Resistivity Tomography ◽

Single Station ◽

Velocity Variations ◽

Spatio Temporal ◽

Velocity Changes ◽

Permafrost Thawing

Permafrost thawing affects mountain slope stability and can trigger hazardous rock falls. As rising temperatures promote permafrost thawing, spatio-temporal monitoring of long-term and seasonal variations in the perennially frozen rock is therefore crucial in regions with high hazard potential. With various infrastructure in the summit area and population in the close vicinity, Mt. Zugspitze in the German/Austrian Alps is such a site and permafrost has been monitored with temperature logging in boreholes and lapse-time electrical resistivity tomography. Yet, these methods are expensive and laborious, and are limited in their spatial and/or temporal resolution.Here, we analyze continuous seismic data from a single station deployed at an altitude of 2700 m a.s.l. in a research station, which is separated by roughly 250 m from the permafrost affected ridge of Mt. Zugspitze. Data are available since 2006 (with some gaps) and reveal high-frequency (>1 Hz) anthropogenic noise likely generated by the cable car stations at the summit. We calculate single-station cross-correlations between the different sensor components and investigate temporal coda wave changes by applying the recently introduced wavelet-based cross-spectrum method. This approach provides time series of the travel time relative to the reference stack as a function of frequency and lag time in the correlation functions. In the frequency and lag range of 1-10 Hz and 0.5-5 s respectively, we find various parts in the coda that show clear annual variations and an increasing trend in travel time over the past 15 years of consideration. Converting the travel time variations to seismic velocity variations (assuming homogeneous velocity changes affecting the whole mountain) results in seasonal velocity changes of up to a few percent and on the order of 0.1% decrease per year. Yet, estimated velocity variations do not scale linearly with lag time, which indicates that the medium changes are localized rather than uniform and that the absolute numbers need to be taken with caution. The annual velocity variations are anti-correlated with the temperature record from the summit but delayed by roughly one month.The phasing of the annual seismic velocity change (relative to the temperature record) is in agreement with a previous study employing lapse-time electrical resistivity tomography. Furthermore, the decreasing trend in seismic velocity happens concurrently with an increasing trend in temperature. The results therefore suggest that the velocity changes are related to seasonal thaw and refreeze and permafrost degradation and thus highlight the potential of seismology for permafrost monitoring. By adding additional receivers and/or a fiber-optic cable for distributed acoustic sensing, hence increasing the spatial resolution, the presented method holds promise for lapse-time imaging of permafrost bodies with high spatio-temporal resolution from passive measurements.

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Detection of repeating earthquakes in the West Bohemia swarm region

10.5194/egusphere-egu2020-16840 ◽

2020 ◽

Author(s):

Ali Salama ◽

Tomas Fischer

Keyword(s):

Fault Zone ◽

Seismic Velocity ◽

Background Activity ◽

Source Parameters ◽

The West ◽

Data Set ◽

Repeating Earthquakes ◽

Waveform Cross Correlation ◽

Cross Correlation Analysis ◽

West Bohemia

&#160;&#160;&#160;Repeating earthquakes, sequences of microseismic events with highly similar seismograms and magnitudes, suggest quasi-periodic rupturing of the same asperity. They are observed on creeping fault segments surrounded by aseismic slip area and also in earthquake swarms. However, so far, they have not been documented in the West Bohemia/Vogtland seismic swarm area. These local swarms consist of thousands of ML < 4 events occurring along a small area of fault zone with repeated activation of some patches during the swarms and weak background activity in the intermediate periods. Detecting and analyzing the repeating earthquakes would help revealing the continuing background activity and identifying fault areas that are active permanently. This could point to the possible sources of fluids or aseismic creep that are supposed to play significant role in swarm generation. Repeating earthquakes are identified by waveform cross-correlation analysis comparing waveforms of repeaters with continuous seismic data set. We developed efficient detection algorithm to identify repeating earthquakes using selected event templates to reveal continuing seismic activity along the main Nov&#253; Kostel fault zone, namely in the areas with only episodic activity. The results provide a robust basis for routine application to the long-term seismic dataset that will allow also for further applications including analysis of the source parameters of the repeaters and/or detecting possible seismic velocity variations in the focal zone. &#160;

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Volcano Ambient Noise Interferometry in the Caribbean (VANIC)

10.5194/egusphere-egu2020-6058 ◽

2020 ◽

Author(s):

Reinoud Sleeman

Keyword(s):

Ambient Noise ◽

Seismic Velocity ◽

Volcano Seismology ◽

Base Level ◽

Noise Interferometry ◽

Single Station ◽

Cross Correlations ◽

The Caribbean ◽

Velocity Variations ◽

Seismic Networks

The hazardous stratovolcanoes in the Lesser Antilles island arc are monitored with sparse seismic networks. The application of ambient noise interferometry to monitor seismic velocity variations (dv/v) on data from such a sparse instrumented volcanic environment often is a challenge. For the purpose of monitoring it is important a) to analyse the applicability of, and differences between, cross- and single-station cross-correlations, b) to estimate the base level of seismic velocity variations during quiet times and c) to understand the characteristics. Within the EUROVOLC instrument &#8220;Transnational Access (TA)&#8221; a proposal called VANIC was supported to a) use and evaluate different types of ambient noise cross correlations (single stations vs. multiple stations; auto, cross and cross-component correlations) to be applied on seismic recordings from the Guadeloupe seismic network on La Soufriere, b) compare the results with dv/v base level estimates from the sparse Netherlands Caribbean network on The Quill and Mt. Scenery and c) start collaboration between OVSG and KNMI on both monitoring and research levels with a focus on volcano seismology. This presentation will focus is on the results obtained during the TA visit to OVGS.

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Seismic velocity recovery following the 2015 Mw 7.8 Gorkha earthquake, Nepal: Towards a coupled vision of damage and hydrological-induced velocity variations

10.5194/egusphere-egu21-12714 ◽

2021 ◽

Author(s):

Luc Illien ◽

Christoph Sens-Schönfelder ◽

Christoff Andermann ◽

Odin Marc ◽

Kristen Cook ◽

...

Keyword(s):

Seismic Waves ◽

Seismic Velocity ◽

Monsoon Season ◽

Seismic Interferometry ◽

Linear Superposition ◽

Gorkha Earthquake ◽

Ground Shaking ◽

Velocity Variations ◽

Velocity Changes ◽

Induced Velocity

Following the passage of seismic waves, most geomaterials experience non-linear mesoscopic elasticity (NLME). This is described by a drop in elastic moduli that precedes a subsequent recovery of physical properties over a relaxation timescale. Thanks to the development of seismic interferometry techniques that allows for the continuous monitoring of relative seismic velocity changes &#948;v in the subsurface, observations of NLME (&#948;vNLME) in the field are now numerous. In parallel, a growing community uses seismic interferometry to monitor velocity changes induced by seasonal hydrological variations (&#948;vhydro). Monitoring of these variations are often independently done and a linear superposition of both effects is mostly assumed when decomposing the observed &#948;v signal (&#948;v =&#160; &#948;vNLME + &#948;vhydro). However, transient hydrological behaviour following co-seismic ground shaking has been widely reported in boreholes measurements and streamflow, which suggests that&#160; &#948;vhydro may be impacted by the transient variation of material properties caused by NLME. In this presentation, we attempt to characterize the relative seismic velocity variations &#948;v retrieved from a small dense seismic array in Nepal that was deployed in the aftermath of the &#160;2015 Mw 7.8 Gorkha earthquake and that is prone to highly variable hydrological conditions. We first investigated the effect of aftershocks in computing &#948;v at a 10-minute resolution centered around significant ground shaking events. After correcting &#948;v for NLME caused by the Gorkha earthquake and its subsequent aftershocks, we test whether the corresponding residuals are in agreement with the background hydrological behaviour which we inferred from a calibrated hydrological model. This is not the case and we find that transient hydrological properties improve the data description in the early phase after the mainshock. We report three distinct relaxation time scales that are relevant for the recovery of seismic velocity at our field site:&#160; 1. A long time scale activated by the main shock of the Gorkha earthquake (~1 year) 2. A relatively short timescale (1-3 days) that occurs after moderate aftershocks. 3. An intermediate timescale (4-6 months) during the 2015 monsoon season that corresponds to the recovery of the hydrological system. This timescale could correspond to an enhanced permeability caused by Gorkha ground shaking. Our study demonstrates the capability of seismic interferometry to monitor transient hydrological properties after earthquakes at a spatial scale that is not available with classical hydrological measurements. This investigation demands calibrated hydrological models and a framework in which the different forcing of &#948;v are coupled.

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A simple method to evaluate the air-to-ground coupling efficiency: a tool helping the assessment of seismic/infrasonic energy partitioning during an eruption

Earth Planets and Space ◽

10.1186/s40623-021-01510-4 ◽

2021 ◽

Vol 73 (1) ◽

Author(s):

Mie Ichihara ◽

Kazuya Yamakawa ◽

Dan Muramatsu

Keyword(s):

Response Function ◽

Seismic Data ◽

Seismic Waves ◽

Seismic Station ◽

Coupling Efficiency ◽

Data Set ◽

Simple Method ◽

Ground Shaking ◽

Acoustic Data ◽

Single Station

AbstractA volcanic eruption transmits both seismic and infrasound signals. The seismo-acoustic power ratio is widely used to investigate the eruption behaviors and the source dynamics. It is often the case that seismic data during an eruption are significantly contaminated or even dominated by ground shaking due to infrasound (air-to-ground signals). To evaluate the contribution of infrasound-originated power in the seismic data, we need a response function of the seismic station to infrasound. It is rare to obtain a seismo-acoustic data set containing only infrasound signals, though it is ideal for calculating the response function. This study proposes a simple way to calculate the response function using seismo-acoustic data containing infrasound and independent seismic waves. The method requires data recorded at a single station and mainly uses the cross-correlation function between the infrasound data and the Hilbert transform of the seismic data. It is tested with data recorded by a station at Kirishima volcano, Japan, of which response function has been constrained. It is shown that the method calculates a proper response function even when the seismic data contain more significant seismic power (or noise) than the air-to-ground signals. The proposed method will be useful in monitoring and understanding eruption behaviors using seismo-acoustic observations.

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A simple method to evaluate the seismic/infrasonic energy partitioning during an eruption using data contaminated by air-to-ground signals

10.21203/rs.3.rs-707480/v1 ◽

2021 ◽

Author(s):

Mie Ichihara ◽

Kazuya Yamakawa ◽

Dan Muramatsu

Keyword(s):

Response Function ◽

Seismic Data ◽

Seismic Waves ◽

Seismic Station ◽

Acoustic Power ◽

Data Set ◽

Simple Method ◽

Ground Shaking ◽

Acoustic Data ◽

Single Station

Abstract A volcanic eruption transmits both seismic waves and infrasound signals. The seismo-acoustic power ratio is widely used to investigate the eruption behaviors and the source dynamics. It is often the case that seismic data during an eruption are significantly contaminated or even dominated by ground shaking due to infrasound (air-to-ground signals). To evaluate the contribution of infrasound-originated power in the seismic data, we need a response function of the seismic station to infrasound. It is rare to obtain a seismo-acoustic data-set containing only infrasound signals, though it is ideal for calculating the response function. This study proposes a simple way to calculate the response function using seismo-acoustic data containing infrasound and independent seismic waves. The method requires data recorded at a single station and mainly uses the cross-correlation function between the infrasound data and the Hilbert transform of the seismic data. It is tested with data recorded by a station at Kirishima volcano, Japan, of which response function has been constrained. It is shown that the method calculates a proper response function even when the seismic data contain more significant seismic power (or noise) than the air-to-ground signals. The proposed method will be useful in monitoring and understanding eruption behaviors using seismo-acoustic observations.

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Seismic velocity recovery in the subsurface: transient damage and groundwater drainage following the 2015 Gorkha earthquake, Nepal

10.31223/x5gd18 ◽

2022 ◽

Author(s):

Luc Illien ◽

Christoph Sens-Schönfelder ◽

Christoph Andermann ◽

Odin Marc ◽

Kristen Cook ◽

...

Keyword(s):

Main Shock ◽

Seismic Velocity ◽

Gorkha Earthquake ◽

Ground Shaking ◽

Transient Behaviour ◽

Shallow Subsurface ◽

2015 Gorkha Earthquake ◽

Unique Maximum ◽

Velocity Variations ◽

Groundwater Drainage

Shallow earthquakes frequently disturb the hydrological and mechanical state of the subsurface, with consequences for hazard and water management. Transient post-seismic hydrological behaviour has been widely reported, suggesting that the recovery of material properties (relaxation) following ground shaking may impact groundwater fluctuations. However, the monitoring of seismic velocity variations associated with earthquake damage and hydrological variations are often done assuming that both effects are independent. In a field site prone to highly variable hydrological conditions, we disentangle the different forcing of the relative seismic velocity variations $\delta v$ retrieved from a small dense seismic array in Nepal in the aftermath of the 2015 Mw 7.8 Gorkha earthquake. We successfully model transient damage effects by introducing a universal relaxation function that contains a unique maximum relaxation timescale for the main shock and the aftershocks, independent of the ground shaking levels. Next, we remove the modeled velocity from the raw data and test whether the corresponding residuals agree with a background hydrological behaviour we inferred from a previously calibrated groundwater model. The fitting of the $\delta v$ data with this model is improved when we introduce transient hydrological properties in the phase immediately following the main shock. This transient behaviour, interpreted as an enhanced permeability in the shallow subsurface, lasts for $\sim$ 6 months and is shorter than the damage relaxation ($\sim$ 1 year). Thus, we demonstrate the capability of seismic interferometry to deconvolve transient hydrological properties after earthquakes from non-linear mechanical recovery.

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Physics-Based Relationship for Pore Pressure and Vertical Stress Monitoring Using Seismic Velocity Variations

Remote Sensing ◽

10.3390/rs13142684 ◽

2021 ◽

Vol 13 (14) ◽

pp. 2684

Author(s):

Eldert Fokker ◽

Elmer Ruigrok ◽

Rhys Hawkins ◽

Jeannot Trampert

Keyword(s):

Pore Pressure ◽

Seismic Velocity ◽

Pressure Head ◽

Groundwater Table ◽

Surface Velocity ◽

Seismic Velocities ◽

Stress Monitoring ◽

Near Surface ◽

Velocity Variations ◽

Velocity Changes

Previous studies examining the relationship between the groundwater table and seismic velocities have been guided by empirical relationships only. Here, we develop a physics-based model relating fluctuations in groundwater table and pore pressure with seismic velocity variations through changes in effective stress. This model justifies the use of seismic velocity variations for monitoring of the pore pressure. Using a subset of the Groningen seismic network, near-surface velocity changes are estimated over a four-year period, using passive image interferometry. The same velocity changes are predicted by applying the newly derived theory to pressure-head recordings. It is demonstrated that the theory provides a close match of the observed seismic velocity changes.

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Attenuation relationships of peak ground motions in the Jazan Region

Arabian Journal of Geosciences ◽

10.1007/s12517-020-06442-z ◽

2021 ◽

Vol 14 (3) ◽

Author(s):

Ali K. Abdelfattah ◽

Abdullah Al-amri ◽

Kamal Abdelrahman ◽

Muhamed Fnais ◽

Saleh Qaysi

Keyword(s):

Saudi Arabia ◽

Ground Motions ◽

Prediction Equation ◽

Peak Ground Velocity ◽

Local Magnitude ◽

Ground Acceleration ◽

Data Set ◽

Hypocentral Distance ◽

Distance Range ◽

Attenuation Relationships

AbstractIn this study, attenuation relationships are proposed to more accurately predict ground motions in the southernmost part of the Arabian Shield in the Jazan Region of Saudi Arabia. A data set composed of 72 earthquakes, with normal to strike-slip focal mechanisms over a local magnitude range of 2.0–5.1 and a distance range of 5–200 km, was used to investigate the predictive attenuation relationship of the peak ground motion as a function of the hypocentral distance and local magnitude. To obtain the space parameters of the empirical relationships, non-linear regression was performed over a hypocentral distance range of 4–200 km. The means of 638 peak ground acceleration (PGA) and peak ground velocity (PGV) values calculated from the records of the horizontal components were used to derive the predictive relationships of the earthquake ground motions. The relationships accounted for the site-correlation coefficient but not for the earthquake source implications. The derived predictive attenuation relationships for PGV and PGA are$$ {\log}_{10}(PGV)=-1.05+0.65\cdotp {M}_L-0.66\cdotp {\log}_{10}(r)-0.04\cdotp r, $$ log 10 PGV = − 1.05 + 0.65 · M L − 0.66 · log 10 r − 0.04 · r , $$ {\log}_{10}(PGA)=-1.36+0.85\cdotp {M}_L-0.85\cdotp {\log}_{10}(r)-0.005\cdotp r, $$ log 10 PGA = − 1.36 + 0.85 · M L − 0.85 · log 10 r − 0.005 · r , respectively. These new relationships were compared to the grand-motion prediction equation published for western Saudi Arabia and indicate good agreement with the only data set of observed ground motions available for an ML 4.9 earthquake that occurred in 2014 in southwestern Saudi Arabia, implying that the developed relationship can be used to generate earthquake shaking maps within a few minutes of the event based on prior information on magnitudes and hypocentral distances taking into considerations the local site characteristics.

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On the reliability of PKIIKP phase identification at a single station

10.5194/egusphere-egu21-6554 ◽

2021 ◽

Author(s):

Olga Usoltseva ◽

Vladimir Ovtchinnikov

Keyword(s):

Inner Core ◽

Seismic Velocity ◽

Seismic Station ◽

Shear Velocity ◽

Outer Core ◽

Joint Analysis ◽

Time Range ◽

Model Parameters ◽

Phase Identification ◽

Single Station

Study of the contact zone between the inner and outer core represents considerable interest for understanding of properties, structures and dynamic of the Earth's core. One of the sources of the data about the processes proceeding in the top part of the inner core is the seismic wave PKIIKP once reflected from an undersize inner core boundary. Amplitudes of these waves are sensitive to the shear velocity in the top part of the inner core and are small. Therefore their identification at a single seismic station is not reliable without application of additional methods of analysis. Significant in this regard is the discussion about the source (in inner core or in mantle) of anomalous arrivals detected at the TAM station in North Africa [1,2] in the time range of PKIIKP phase.To estimate influence of model parameters (S and P seismic velocity) on the characteristics of PKIIKP wave (amplitude and travel time) we calculated sensitivity kernels for upper mantle and inner core for dominant period 1.2 s, azimuth step 0.2 degrees and radius step 20 km by using DSM Kernel Suite algorithm. It was revealed that PKIIKP amplitude is more sensitivities to mantle heterogeneities than to inner core ones. For reducing the effects of the overlying structures we suppose to use &#1072; joint analysis PKIIKP and pPKIIKP waves. With this approach, an incorrect identification of the PKIIKP wave is most likely excluded. We demonstrate the effectiveness of the approach on the example of processing the seismogram of the 11.02.2015 earthquake re&#1089;orded at the GZH station in China at a distance of 179.4 degrees.1. Wang W., Song X. Analyses of anomalous amplitudes of antipodal PKIIKP waves, EaPP. 2019. V. 3. P. 212-217. doi: 10.26464/epp20190232. Tsuboi S., Butler R. Inner core differential rotation inferred from antipodal seismic observations, PEPI, 2020. V.301. 106451.

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