The Finnish National Seismic Network: Toward Fully Automated Analysis of Low-Magnitude Seismic Events

Veikkolainen, Toni; Kortström, Jari; Vuorinen, Tommi; Salmenperä, Ilmo E.; Luhta, Tuija; Mäntyniemi, Päivi; Hillers, Gregor; Tiira, Timo

doi:10.1785/0220200352

Cited by 12 publications

(6 citation statements)

References 25 publications

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“…Stations operated by ISUH include the three Finnish National Seismic Network (FNSN) broadband stations MEF, NUR, PVF (black circles in Fig. 1) [Veikkolainen et al, 2021a], five broadband stations HEL1 to HEL5 deployed in 2016 and 2017 to monitor the seismicity associated with the reservoir development, and three new broadband stations KUNI, LAUT, VUOS (dark blue circles in Fig. 1) of the HelsinkiNet that were commissioned in 2019 and 2020 by the City of Helsinki for monitoring purposes.…”

Section: Permanent Stationsmentioning

confidence: 99%

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A Seismic Network to Monitor the 2020 EGS Stimulation in the Espoo/Helsinki Area, Southern Finland

Rintamäki

Hillers

Vuorinen

et al. 2021

Seismological Research Letters

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We present the deployment of a seismic network in the Helsinki capital area of Finland that was installed to monitor the response to the second stimulation phase of an ∼6-kilometer-deep enhanced geothermal system in 2020. The network consists of a dozen permanent broadband stations and more than 100, predominantly short-period, temporary stations. This 2020 deployment is characterized by a mix of single stations and arrays with diverse configurations. It covers a larger area and exhibits a smaller azimuthal gap compared with the network that monitored the first stimulation in 2018. We surveyed the outcropping rocks at one of the large array sites to study surface expressions of shear or weakness zones that are possibly connected to the stimulated volume at depth. We link the relatively large number of macroseismic reports received during the stimulation to an increased public awareness of the project together with an increased sensitivity because the second stimulation occurred during the local COVID-19 mobility restrictions. The spatial distribution of the reports seems to be controlled by the radiation pattern of the induced earthquakes and hence by the stress state in the reservoir. The continuous records contain strong energy at high frequencies above 50 Hz that is attributed to anthropogenic processes in the densely populated urban area. However, the exceptionally low attenuation of the bedrock yields good signal-to-noise ratio seismograms of the induced small events, the largest of which was magnitude ML 1.2. The signal quality of the obtained noise correlation functions is similarly very good. The data set has been collected to underpin a wide range of seismic analysis techniques for complementary scientific studies of the evolving reservoir processes and the induced event properties. These scientific studies should inform the legislation and educate the public for transparent decision making around geothermal power generation.

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Section: Permanent Stationsmentioning

confidence: 99%

“…These permanent broadband stations are together referred to as the HE subnetwork in Table 1 and in Figure 3. They are powered by the electric grid and data transmission is continuous [Veikkolainen et al, 2021a].…”

Section: Permanent Stationsmentioning

confidence: 99%

A Seismic Network to Monitor the 2020 EGS Stimulation in the Espoo/Helsinki Area, Southern Finland

Rintamäki

Hillers

Vuorinen

et al. 2021

Seismological Research Letters

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“…Although the low frequency results are less well constrained due to the smaller number of sufficiently large earthquakes, the here observed overall strong frequency dependence suggests a systematic change in the governing relaxation processes across the range of wavelength scales. The significance of these results will benefit from complementary studies of other earthquake sequences in similar environments, for example, in the Rapakivi granite area in southeastern Finland (Luhta et al., 2022), and from a comprehensive analysis of the seismicity across the Fennoscandian Shield (Veikkolainen et al., 2021). Considerable depth dependent variations of

{Q}_{\mathrm{i}}^{-1}

have been estimated using the borehole data from Sweden (Line et al., 1998) using frequencies up to 200 Hz.…”

Section: Discussionmentioning

confidence: 99%

“…This focus is now widened by an increased interest in geothermal energy production. The data collected in this context can inform common practice (Fülöp et al., 2020), which assumes neutral spectral acceleration amplification at the locations of the broadband stations of the Finnish National Seismic Network or a regional network extension (Kortström et al., 2018; Veikkolainen et al., 2021). These are typically quality installations at surface hard rock sites, which means all installations are considered to be of reference very hard rock site quality.…”

Section: Discussionmentioning

confidence: 99%

“…We use envelopes of seismograms from 233 events in 2018 and 22 events in 2020 in the M L 0.0 to M L 1.8 range that were recorded by local networks consisting of permanent and temporary borehole and surface stations (Hillers et al., 2020; Kwiatek et al., 2019; Rintamäki et al., 2021). The study area is located in the southern Fennoscandian Shield, where the level of natural background seismicity is relatively low (Veikkolainen et al., 2021). The Finnish National Seismic Network detects between 10,000 and 20,000 seismic events per year.…”

Section: Introductionmentioning

confidence: 99%

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Induced Earthquake Source Parameters, Attenuation, and Site Effects From Waveform Envelopes in the Fennoscandian Shield

et al. 2023

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We analyze envelopes of 233 and 22 ML0.0 to ML1.8 earthquakes induced by two geothermal stimulations in the Helsinki, Finland, metropolitan area. We separate source spectra and site terms and determine intrinsic attenuation and the scattering strength of shear waves in the 3–200 Hz frequency range using radiative transfer based synthetic envelopes. Displacement spectra yield scaling relations with a general deviation from self‐similarity, with a stronger albeit more controversial signal from the weaker 2020 stimulation. The 2020 earthquakes also tend to have a smaller local magnitude compared to 2018 earthquakes with the same moment magnitude. We discuss these connections in the context of fluid effects on rupture speed or medium properties. Site terms demonstrate that the spectral amplification relative to two reference borehole sites is not neutral at the other sensors; largest variations are observed at surface stations at frequencies larger than 30 Hz. Intrinsic attenuation is exceptionally low with Qi−1 ${Q}_{\mathrm{i}}^{-1}$ values down to 2.4 × 10−5 at 20 Hz, which allows the observation of a diffuse reflection at the ∼50 km deep Moho. Scattering strength is in the range of globally observed data with Qnormalsnormalc−1 ${Q}_{\mathrm{s}\mathrm{c}}^{-1}$ between 10−3 and 10−4. The application of the employed Qopen analysis program to the 2020 data in a retrospective monitoring mode demonstrates its versatility as a seismicity processing tool. The diverse results have implications for scaling relations, hazard assessment and ground motion modeling, and imaging and monitoring using ballistic and scattered wavefields in the crystalline Fennoscandian Shield environment.

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Potential of the Arkhangelsk seismic network for European Arctic monitoring

Antonovskaya,

Konechnaya,

Morozova

et al. 2024

Earthquake Science

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The Finnish National Seismic Network: Toward Fully Automated Analysis of Low-Magnitude Seismic Events

Cited by 12 publications

References 25 publications

A Seismic Network to Monitor the 2020 EGS Stimulation in the Espoo/Helsinki Area, Southern Finland

A Seismic Network to Monitor the 2020 EGS Stimulation in the Espoo/Helsinki Area, Southern Finland

Induced Earthquake Source Parameters, Attenuation, and Site Effects From Waveform Envelopes in the Fennoscandian Shield

Potential of the Arkhangelsk seismic network for European Arctic monitoring

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