Revisiting Svenskby, Southeastern Finland: Communications Regarding Low-Magnitude Earthquakes in 1751–1752

This investigation examines the contemporary documentation of a sequence of low-magnitude earthquakes at the fringes of the Kingdom of Sweden, today Southeastern Finland, in 1751–1752. A total of 11 pages of original correspondence sent from the target village of Svenskby to the Swedish capital Stockholm are reviewed. Newspaper accounts from Sweden and Russia are included in the analysis, and a timeline of the reporting is constructed. A newly created catalog shows over 30 distinct events between the end of October and December 1751 (Julian calendar). The assignment of macroseismic intensity to the earthquakes is hampered by loud acoustic effects that accompany and/or constitute the observations. Maximum intensities are assessed at IV–V (European Macroseismic Scale 1998), and maximum macroseismic magnitudes in the range of MM1.9–2.4, and were probably observed at short epicentral distances close to the ground surface. Comparisons to macroseismic data related to instrumentally recorded earthquakes in the region support the notion of low magnitudes. The data from 1751 provide an analog to modern macroseismic observations from geothermal stimulation experiments. Such experiments have acted as a spur for considering seismic risk from low-magnitude earthquakes whose consequences have seldom previously been a matter for concern

Revisiting Svenskby, Southeastern Finland: Communications Regarding Low-Magnitude Earthquakes in 1751–1752

This investigation examines the contemporary documentation of a sequence of low-magnitude earthquakes at the fringes of the Kingdom of Sweden, today Southeastern Finland, in 1751–1752. A total of 11 pages of original correspondence sent from the target village of Svenskby to the Swedish capital Stockholm are reviewed. Newspaper accounts from Sweden and Russia are included in the analysis, and a timeline of the reporting is constructed. A newly created catalog shows over 30 distinct events between the end of October and December 1751 (Julian calendar). The assignment of macroseismic intensity to the earthquakes is hampered by loud acoustic effects that accompany and/or constitute the observations. Maximum intensities are assessed at IV–V (European Macroseismic Scale 1998), and maximum macroseismic magnitudes in the range of MM1.9–2.4, and were probably observed at short epicentral distances close to the ground surface. Comparisons to macroseismic data related to instrumentally recorded earthquakes in the region support the notion of low magnitudes. The data from 1751 provide an analog to modern macroseismic observations from geothermal stimulation experiments. Such experiments have acted as a spur for considering seismic risk from low-magnitude earthquakes whose consequences have seldom previously been a matter for concern

Makroseismologian antia Pohjolan seismisyyden tutkimukselle

This work focuses on the role of macroseismology in the assessment of seismicity and probabilistic seismic hazard in Northern Europe. The main type of data under consideration is a set of macroseismic observations available for a given earthquake. The macroseismic questionnaires used to collect earthquake observations from local residents since the late 1800s constitute a special part of the seismological heritage in the region. Information of the earthquakes felt on the coasts of the Gulf of Bothnia between 31 March and 2 April 1883 and on 28 July 1888 was retrieved from the contemporary Finnish and Swedish newspapers, while the earthquake of 4 November 1898 GMT is an example of an early systematic macroseismic survey in the region. A data set of more than 1200 macroseismic questionnaires is available for the earthquake in Central Finland on 16 November 1931. Basic macroseismic investigations including preparation of new intensity data point (IDP) maps were conducted for these earthquakes. Previously disregarded usable observations were found in the press. The improved collection of IDPs of the 1888 earthquake shows that this event was a rare occurrence in the area. In contrast to earlier notions it was felt on both sides of the Gulf of Bothnia. The data on the earthquake of 4 November 1898 GMT were augmented with historical background information discovered in various archives and libraries. This earthquake was of some concern to the authorities, because extra fire inspections were conducted in three towns at least, i.e. Tornio, Haparanda and Piteå, located in the centre of the area of perceptibility. This event posed the indirect hazard of fire, although its magnitude around 4.6 was minor on the global scale. The distribution of slightly damaging intensities was larger than previously outlined. This may have resulted from the amplification of the ground shaking in the soft soil of the coast and river valleys where most of the population was found. The large data set of the 1931 earthquake provided an opportunity to apply statistical methods and assess methodologies that can be used when dealing with macroseismic intensity. It was evaluated using correspondence analysis. Different approaches such as gridding were tested to estimate the macroseismic field from the intensity values distributed irregularly in space. In general, the characteristics of intensity warrant careful consideration. A more pervasive perception of intensity as an ordinal quantity affected by uncertainties is advocated. A parametric earthquake catalogue comprising entries from both the macroseismic and instrumental era was used for probabilistic seismic hazard assessment. The parametric-historic methodology was applied to estimate seismic hazard at a given site in Finland and to prepare a seismic hazard map for Northern Europe. The interpretation of these results is an important issue, because the recurrence times of damaging earthquakes may well exceed thousands of years in an intraplate setting such as Northern Europe. This application may therefore be seen as an example of short-term hazard assessment.Om makroseismologins roll vid studiet av Fennoskandias seismicitet Denna avhandling fokuserar på makroseismologi. Den utgör del av icke-instrumentell seismologi som sysslar med skriftliga dokument om jordskalvseffekterna i synnerhet i bebyggd miljö. Makroseismiska iakttagelser omspänner tidsmässigt betydligt längre perioder än instrumentella registreringar. Den makroseismiska undersökningens uppgift är att söka skriftliga källor om jordskalv i forntid och textkritiskt bearbeta väsentlig information ur diverse arkivfynd. Jordstötarna mellan den 31 mars och 2 april 1883 samt den 28 juli 1888 väckte uppmärksamhet i Österbotten och Västerbotten. Alla tillgängliga uppgifter om dessa skalv insamlades ur dåtidens dagspress och utarbetades till kartor som visar var intensiteten var störst och hur den avtog i olika riktningar. (Makroseismisk) intensitet är ett mått på effekternas styrka och måste skiljas från begreppet magnitud, som är unikt för varje jordskalv. Året 1888 var det påverkade området mera vidsträckt än man tidigare trott. Det omfattade båda sidorna av norra Bottenhavet. Jordskalvet den 5 november 1898 (lokal tid) är ett exempel på en tidig systematisk makroseismisk utredning i Norden: särskilda frågeformulär distribuerades till befolkningen i norra Sverige och Finland för att insamla observationer. Dessa meddelanden kompletterades med tidningsnotiser samt geofysikaliska och historiska fakta om området. Skalvet förorsakade skador i murar kring norra Bottenviken, och extra brandbesiktningar förrättades åtminstone i Torneå, Haparanda och Piteå. I Torneå pågick brandbesiktning i tre dagar och visade att sprickor och brott hade uppstått i 11% av skorstenarna i staden. Den indirekta risken för eldsvådor fanns trots att skalvets magnitud var omkring 4.6 det vill säga lindrig magnitud på världsskalan. Stark jordskakning förekom på ett större område än vad en äldre karta utvisar. Detta ger anledning till att flytta skalvets epicentrum västerut. Det kan ha varit beläget i Tornedalen. Skakningen kan ha tilltagit i styrka i lösa jordarter vid kusten och älvstränder där de flesta iakttagarna var bosatta. Ett stort antal makroseismiska frågeblanketter – ca 1200 – insamlades strax efter jordskalvet i mellersta Finland den 16 november 1931. Statistiska metoder tillämpades på materialet för att så objektivt som möjligt estimera vilka intensiteter som förekommit på olika orter och för att avgränsa områden med olika intensitet från varandra. Kring sekelskiftet för ett hundra år sedan utgjorde Finlands omnejd en mera högseismisk region än nuförtiden, så en imponerande mängd naturföreteelser kan studeras med hjälp av makroseismologi. Dock framgår ingen slutgiltig uppfattning om de allra kraftigaste jordbävningarna som där inträffade.Tämä työ kohdistuu makroseismologiaan. Se on ei-instrumentaalisen seismologian osa, joka tutkii kirjallisia merkintöjä maanjäristysten vaikutuksista etenkin rakennettuun ympäristöön. Makroseismiset havainnot ulottuvat ajassa paljon kauemmas taaksepäin kuin laiterekisteröinnit. Alan tutkimukseen kuuluu menneisyyden maanjäristyksiä käsittelevien tietolähteiden hakeminen ja käyttökelpoisten tietojen kokoaminen erilaisista arkistolöydöistä tekstikriittisen analyysin avulla. Maaliskuun 31. ja huhtikuun 2. päivän välillä 1883 sekä 28. heinäkuuta 1888 Pohjanlahden rannikoilla huomiota herättäneistä maanjäristyksistä tehtiin makroseisminen perustutkimus. Kaikki saatavilla oleva tieto koottiin ajankohtien lehdistöstä ja työstettiin kartoiksi, joista käy ilmi, missä intensiteetti oli suurimmillaan ja miten se vaimeni eri suuntiin. (Makroseisminen) intensiteetti kuvaa järistysvaikutusten voimakkuutta ja eroaa tyystin magnitudista, joka on ainutkertainen kullekin maanjäristykselle. Vuonna 1888 järistyksen tuntuvuusalue oli laajempi kuin aikaisemmin on arveltu, sillä se käsitti pohjoisen Pohjanlahden molemmat rannikot. Maanjäristys 5. marraskuuta 1898 (paikallista aikaa) on esimerkkinä varhaisesta järjestelmällisestä makroseismisestä selvityksestä Pohjolassa: tuntuvuushavaintoja kerättiin tuolloin asukkailta erityisillä kyselykaavakkeilla. Tässä työssä näitä tiedonantoja täydennettiin sanomalehtien uutisilla sekä geofysikaalisilla ja historiallisilla taustatiedoilla alueesta. Järistys vaurioitti muureja Perämeren pohjukassa, minkä vuoksi ylimääräisiä palotarkastuksia toimitettiin ainakin Torniossa, Haaparannassa ja Piitimessä. Torniossa palotarkastus vei kolme päivää, ja rakoilua ja halkeamia löytyi 11 prosentista kaupungin savupiipuista. Tulipalot olivat epäsuora järistysuhka, vaikka järistyksen magnitudi oli suuruusluokkaa 4.6, eli vähäinen maailman mittakaavassa. Voimakasta maanliikettä esiintyi laajemmalla alueella kuin aikaisemman kartan mukaan. Tämän vuoksi on aiheellista siirtää järistyskeskusta länteen päin. Se saattoi sijaita Tornionjokilaaksossa. Tärinä saattoi voimistua irtonaisissa maalajeissa rannikolla ja jokivarsilla, missä suurin osa havaitsijoista asui. Keski-Suomessa 16. marraskuuta 1931 sattuneesta maanjäristyksestä on saatavilla tuota pikaa sen jälkeen kerätty suuri havaintoaineisto, noin 1200 kyselylomaketta. Aineistoon sovellettiin tilastollisia menetelmiä, jotta voitiin arvioida mahdollisimman objektiivisesti, kuinka suuria intensiteettejä esiintyi eri paikoissa ja rajata eri intensiteetin alueita toisistaan. Vuosisadan vaihteessa satakunta vuotta sitten Suomen lähialueiden seismisyystaso oli korkeampi kuin nykyään, joten makroseismologian keinoin voidaan tutkia vaikuttavia seismisyysilmiöitä. Tietojen perusteella ei kuitenkaan saavuteta käsitystä seudun kaikkein voimakkaimmista maanjäristyksistä

The effects of climate change on Baltic salmon : Framing the problem in collaboration with expert stakeholders

In the Baltic Sea region, salmon are valued for the ecological, economic, and cultural benefits they provide. However, these fish are threatened due to historical overfishing, disease, and reduced access to spawning rivers. Climate change may pose another challenge for salmon management. Therefore, we conducted a problem-framing study to explore the effects climate change may have on salmon and the socio-ecological system they are embedded within. Addressing this emerging issue will require the cooperation of diverse stakeholders and the integration of their knowledge and values in a contentious management context. Therefore, we conducted this problem framing as a participatory process with stakeholders, whose mental models and questionnaire responses form the basis of this study. By framing the climate change problem in this way, we aim to provide a holistic understanding of the problem and incorporate stakeholder perspectives into the management process from an early stage to better address their concerns and establish common ground. We conclude that considering climate change is relevant for Baltic salmon management, although it may not be the most pressing threat facing these fish. Stakeholders disagree about whether climate change will harm or benefit salmon, when it will become a relevant issue in the Baltic context, and whether or not management efforts can mitigate any negative impacts climate change may have on salmon and their fishery. Nevertheless, by synthesizing the stakeholders' influence diagrams, we found 15 themes exemplifying: (1) how climate change may affect salmon, (2) goals for salmon management considering climate change, and (3) strategies for achieving those goals. Further, the stakeholders tended to focus on the riverine environment and the salmon life stages occurring therein, potentially indicating the perceived vulnerability of these life stages to climate change. Interestingly, however, the stakeholders tended to focus on traditional fishery management measures, like catch quotas, to meet their goals for these fish considering climate change. Further, social variables, like “politics,” “international cooperation,” and “employment” comprised a large proportion of the stakeholders' diagrams, demonstrating the importance of these factors for salmon management.Peer reviewe

How to deal with sparse macroseismic data : Reflections on earthquake records and recollections in the Eastern Baltic Shield

This study discusses the scope of historical earthquake analysis in low-seismicity regions. Examples of non-damaging earthquake reports are given from the Eastern Baltic (Fennoscandian) Shield in north-eastern Europe from the 16th to the 19th centuries. The information available for past earthquakes in the region is typically sparse and cannot be increased through a careful search of the archives. This study applies recommended rigorous methodologies of historical seismology developed using ample data to the sparse reports from the Eastern Baltic Shield. Attention is paid to the context of reporting, the identity and role of the authors, the circumstances of the reporting, and the opportunity to verify the available information by collating the sources. We evaluate the reliability of oral earthquake recollections and develop criteria for cases when a historical earthquake is attested to by a single source. We propose parametric earthquake scenarios as a way to deal with sparse macroseismic reports and as an improvement to existing databases.This study discusses the scope of historical earthquake analysis in low-seismicity regions. Examples of non-damaging earthquake reports are given from the Eastern Baltic (Fennoscandian) Shield in north-eastern Europe from the 16th to the 19th centuries. The information available for past earthquakes in the region is typically sparse and cannot be increased through a careful search of the archives. This study applies recommended rigorous methodologies of historical seismology developed using ample data to these sparse reports from the Eastern Baltic Shield. Attention is paid to the context of the reporting, the identity and role of the authors, the circumstances of the reporting, and the opportunity to verify the available information by collating the sources. We evaluate the reliability of oral earthquake recollections and develop criteria for cases when a historical earthquake is attested to by a single source. We propose parametric earthquake scenarios as a way to deal with sparse macroseismic reportsand as an improvement to existing databases.Peer reviewe

Valorisation of probabilistic seismic hazard results in Finland (VALERI)

Probabilistic seismic hazard analysis (PSHA) is the standard method to assess seismic hazard for nuclear power plants (NPPs). In Finland, the median confidence seismic hazard at annual frequency of exceedance (AFE) 10-5 is used for designbasis earthquake (DBE), with a minimum threshold of the horizontal peak-ground acceleration of 0.1g. Exceptional earthquakes for design extension conditions (DECC) are proposed with median confidence at AFE 10-7/year (STUK, 2019). In this work, we explore the possibilities of DBE being anchored to other confidence level hazards, since the use of median is the minority position in Europe. We outline PSHA as a tool for hazard calculations, and how hazards are used in risk assessment and risk-informed decision-making. We particularly focus on the treatment of uncertainties and arguments about the mean and fixed-confidence hazards. The goal is to probe if regulatory transition away from median confidence hazard is (i) desirable, (ii) possible and (iii) identify the foreseeable difficulties. We discuss possible options for DBE and DEC C, for the consideration of the different stakeholders. Since the use of median hazard has a long tradition in Finland, an update would be no trivial undertaking

Valorization of probabilistic seismic hazard results in Finland

Probabilistic seismic hazard analysis (PSHA) is currently the standard method for assessing seismic hazards for nuclear power plants (NPPs) in Finland. To obtain values of ground-motion parameters for design purposes, two decisions are made regarding which annual frequency of exceedance (AFE) should be adopted and from which hazard curve the ground-motion value should be read for the design-basis earthquake (DBE) and the design-extension condition earthquake (DEC EQ, DEC C for short). The current regulatory status in Finland, given in the guide YVL B.7 (STUK 2019) by the Radiation and Nuclear Safety Authority of Finland (STUK), is that the median- confidence seismic hazard at AFE 10−5 is used for DBEs at NPPs with a minimum horizontal peak-ground acceleration (PGA) of 0.1 g. The high variability of ground-motion shaking patterns and various examples of exceedance of the DBE ground motion from that of natural earthquakes throughout the world have resulted in upgrades to meet new definitions of the requirements for ground motion beyond that of DBEs. Exceptional earthquake effects, with an estimated frequency of occurrence less than 10−5/year are postulated in DEC C for NPPs in Finland. Here, we outline the PSHA and its consequent use in risk assessment and risk-informed decision-making. We review arguments about the mean and median hazard curves in the PSHA. We draw particularly on the outcomes of the SENSEI (SENsitivity study of SEIsmic hazard prediction in Finland) project conducted under the auspices of STUK in 2019−2020, present new figures based on the SENSEI set of hazard calculations, and analyze them. We focus on the ratio of the mean and median hazard of PGA, spectral acceleration at 1 Hz, 5 Hz, and 25 Hz at AFE levels 10−4, 10−5, 10−6, 10−7 and 10−8. We analyze possible options for DBE and DEC C for consideration of the various stakeholders. Since the use of median hazards has a long tradition in Finland, an update is no trivial undertaking. The suite of options is not necessarily exhaustive

Testing the Environmental Seismic Intensity Scale on Data Derived from the Earthquakes of 1626, 1759, 1819, and 1904 in Fennoscandia, Northern Europe

Earthquake environmental effects (EEEs) were compiled for the earthquakes of 1626, 1759, 1819, and 1904 in the Fennoscandian Peninsula, northern Europe. The principal source of information was the contemporary newspaper press. Macroseismic questionnaires collected in 1759 and 1904 were also consulted. We prepared maps showing newly discovered EEEs together with previously known EEEs and analyzed their spatial distribution. We assigned intensities based on the 2007 Environmental Seismic Intensity (ESI) scale to 27 selected localities and compared them to intensities assigned based on the 1998 European Macroseismic Scale. While the overall agreement between the scales is good, intensities may remain uncertain due to the sparsity of written documentation. The collected data sets are most probably incomplete but still show that EEEs are not unprecedented cases in the target region. The findings include landslides and rockfalls as well as cascade effects with a risk potential and widespread water movements up to long distances. The winter earthquake of 1759 cracked ice over a large area. This investigation demonstrates that the ESI scale also has practical importance for regions with infrequent EEEs

Valorization of probabilistic seismic hazard results in Finland

Probabilistic seismic hazard analysis (PSHA) is currently the standard method for assessing seismic hazards for nuclear power plants (NPPs) in Finland. To obtain values of ground-motion parameters for design purposes, two decisions are made regarding which annual frequency of exceedance (AFE) should be adopted and from which hazard curve the ground-motion value should be read for the design-basis earthquake (DBE) and the design-extension condition earthquake (DEC EQ, DEC C for short). The current regulatory status in Finland, given in the guide YVL B.7 (STUK 2019) by the Radiation and Nuclear Safety Authority of Finland (STUK), is that the median- confidence seismic hazard at AFE 10−5 is used for DBEs at NPPs with a minimum horizontal peak-ground acceleration (PGA) of 0.1 g. The high variability of ground-motion shaking patterns and various examples of exceedance of the DBE ground motion from that of natural earthquakes throughout the world have resulted in upgrades to meet new definitions of the requirements for ground motion beyond that of DBEs. Exceptional earthquake effects, with an estimated frequency of occurrence less than 10−5/year are postulated in DEC C for NPPs in Finland. Here, we outline the PSHA and its consequent use in risk assessment and risk-informed decision-making. We review arguments about the mean and median hazard curves in the PSHA. We draw particularly on the outcomes of the SENSEI (SENsitivity study of SEIsmic hazard prediction in Finland) project conducted under the auspices of STUK in 2019−2020, present new figures based on the SENSEI set of hazard calculations, and analyze them. We focus on the ratio of the mean and median hazard of PGA, spectral acceleration at 1 Hz, 5 Hz, and 25 Hz at AFE levels 10−4, 10−5, 10−6, 10−7 and 10−8. We analyze possible options for DBE and DEC C for consideration of the various stakeholders. Since the use of median hazards has a long tradition in Finland, an update is no trivial undertaking. The suite of options is not necessarily exhaustive