Probabilistic Seismic Hazard Assessment (Horizontal PGA) for Fennoscandia Using the Logic Tree Approach for Regionalization and Nonregionalization Models

Wahlström, Rutger; Grünthal, Gottfried

doi:10.1785/gssrl.72.1.33

“…Therefore, it may be sensible to calculate the depth distribution using data from larger areas, e.g. see Wahlström and Grünthal [2001]. The strong influence of this parameter in regions where the span of focal depths is large is demonstrated by Atkinson and Charlwood [1983].…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Sensitivity of Parameters for Probabilistic Seismic Hazard Analysis Using a Logic Tree Approach

Grünthal

¹

,

Wahlström

²

2001

Journal of Earthquake Engineering

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The sensitivity of different parameters used in probabilistic seismic hazard calculation is investigated by different logic tree runs with alternative magnitude sets, source zone models and attenuation relations, and with different sets of values for the seismicity parameters and the σ-value. Also the influence from the different parameters on the hazard uncertainty, represented by fractiles, is investigated. The calculations are made for peak ground acceleration at a site near Aachen in the Lower Rhine Embayment. The model where the site is located in a larger source zone gives lower hazard values. This is typical for the case where the seismicity near the site is high relative to its surrounding. The hazard curves for the different attenuation functions are similar, an effect of the similarity of the functions themselves. However, a large sensitivity of this parameter is indicated for small mean return periods. An increased σ-value implies a moderate increase of the hazard at long mean return periods. The hazard is increasing for decreased focal depth, decreased ß-value and increased maximum expected magnitude, respectively. However, the effects are noteworthy only at low hazard levels for variations in the focal depth and to some extent in the maximum expected magnitude. Finally, decreasing the minimum magnitude thought to be of engineering relevance causes a drastic increase of the hazard at small mean return periods.

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“…Therefore, it may be sensible to calculate the depth distribution using data from larger areas, e.g. see Wahlström and Grünthal [2001]. The strong influence of this parameter in regions where the span of focal depths is large is demonstrated by Atkinson and Charlwood [1983].…”

Section: Conclusion and Discussionmentioning

confidence: 99%

Untitled

Grünthal¹

2001

J. Earth. Eng.

1

0

View full text Add to dashboard Cite

The sensitivity of different parameters used in probabilistic seismic hazard calculation is investigated by different logic tree runs with alternative magnitude sets, source zone models and attenuation relations, and with different sets of values for the seismicity parameters and the σ-value. Also the influence from the different parameters on the hazard uncertainty, represented by fractiles, is investigated. The calculations are made for peak ground acceleration at a site near Aachen in the Lower Rhine Embayment. The model where the site is located in a larger source zone gives lower hazard values. This is typical for the case where the seismicity near the site is high relative to its surrounding. The hazard curves for the different attenuation functions are similar, an effect of the similarity of the functions themselves. However, a large sensitivity of this parameter is indicated for small mean return periods. An increased σ-value implies a moderate increase of the hazard at long mean return periods. The hazard is increasing for decreased focal depth, decreased ß-value and increased maximum expected magnitude, respectively. However, the effects are noteworthy only at low hazard levels for variations in the focal depth and to some extent in the maximum expected magnitude. Finally, decreasing the minimum magnitude thought to be of engineering relevance causes a drastic increase of the hazard at small mean return periods.

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“…The Wahlström and Grünthal (2000) and follow-up Wahlström and Grünthal (2001) studies perform full probabilistic seismic hazard assessments for Fennoscandia using the FENCAT catalogue. Wahlström and Grünthal (2001) apply two different magnitude homogenization schemes.…”

Section: Previous Seismic Hazard Assessments For Swedenmentioning

confidence: 99%

Probabilistic Seismic Hazard Assessment of Sweden

Joshi,

Lund,

Roberts

2023

Preprint

0

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Abstract. Assessing seismic hazard in stable continental regions (SCR) such as Sweden poses unique challenges compared to active seismic regions. With diffuse seismicity, low seismicity rate, few large magnitude earthquakes and little strong motion data, estimating recurrence parameters and determining appropriate attenuation relationships is challenging. This study presents a probabilistic seismic hazard assessment of Sweden based on a recent earthquake catalogue which includes a large number of events with magnitudes ranging from 5.9 to -1.4, enabling recurrence parameters to be calculated for more source areas than in previous studies, and with less uncertainty. Recent ground motion models developed specifically for stable continental regions, including Fennoscandia, are used in logic trees accounting for their uncertainty and the hazard is calculated using the OpenQuake engine. The results are presented in the form of mean peak ground acceleration (PGA) maps at 475 and 2500 year return periods and hazard curves for four seismically active areas in Sweden. We find the highest hazard in the northernmost part of the country, in the post-glacial fault province. This is in contrast to previous studies, which have not considered the high seismic activity on the post-glacial faults. We also find relatively high hazard along the northeast coast and in southwestern Sweden, whereas the southeast and the mountain region to the northwest have low hazard. For a 475 year return period we estimate the highest PGAs to be 0.04–0.05 g, in the far north, and for a 2500 year return period it is 0.1–0.15 g in the same area. Significant uncertainties remain to be addressed in regards to the SCR seismicity in Sweden, including the homogenization of small local magnitudes with large moment magnitudes, the occurrence of large events in areas with little prior seismicity and the uncertainties surrounding the potential for large earthquakes on the post-glacial faults in northern Fennoscandia.

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Probabilistic Seismic Hazard Assessment (Horizontal PGA) for Fennoscandia Using the Logic Tree Approach for Regionalization and Nonregionalization Models

Abstract: Originally published as:Wahlström, R., Grünthal, G. (2001): Probabilistic seismic hazard assessment (horizontal PGA) for Fennoscandia using the logic tree approach for regionalization and nonregionalization models.

Cited by 11 publications

References 22 publications

Sensitivity of Parameters for Probabilistic Seismic Hazard Analysis Using a Logic Tree Approach

Sensitivity of Parameters for Probabilistic Seismic Hazard Analysis Using a Logic Tree Approach

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Probabilistic Seismic Hazard Assessment of Sweden

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