Regional spectral scaling relations of source parameters for earthquakes in the Baltic Shield

Kim, W.-Y.; Wahlström, Rutger; Uski, Marja

doi:10.1016/0040-1951(89)90210-2

Cited by 26 publications

(19 citation statements)

References 15 publications

(16 reference statements)

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“…Some of the outliers also appear to have the highest stress drops, as discussed in a forthcoming article (Tan and Helmberger, manuscript in preparation). The slope of 1.12 agrees with the previous results of Bakun (1984), Vidal and Mungúia (1991), Kim et al (1989), and Bindi et al (2001) for events of similar size. However, we do not observe the continuous log(M 0 ) versus M L curvature as suggested by Hanks and Boore (1984).…”

Section: Resultssupporting

confidence: 90%

A New Method for Determining Small Earthquake Source Parameters Using Short-Period P Waves

Tan¹,

Helmberger²

2007

Bulletin of the Seismological Society of America

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We developed a new technique of inverting short-period (0.5-2 Hz) P waveforms for determining small earthquake (M Ͻ3.5) focal mechanisms and moments, where magnitude ϳ4 events with known source mechanisms are used to calibrate the "unmodeled" structural effect. The calibration is based on a waveform cluster analysis, where we show that clustered events of different sizes, for example, M ϳ4 versus M ϳ2, display similar signals in the short-period (SP, 0.5-2 Hz) frequency band, implying propagational stability. Since both M ϳ4 and M ϳ2 events have corner frequencies higher than 2 Hz, they can be treated as point sources, and the "unmodeled" structural effect on the SP P waves can be derived from the magnitude 4 events with known source mechanisms. Similarly, well-determined magnitude 2's can provide calibration for studying even smaller events at higher frequencies, for example, 2-8 Hz. In particular, we find that the "unmodeled" structural effect on SP P waves is mainly an amplitude discrepancy between data and 1D synthetics. The simple function of "amplitude amplification factor" (AAF) defined as the amplitude ratio between data and synthetics provides useful calibration, in that the AAFs derived from different clustered events appear consistent, hence stable and mechanism independent. We take a grid-search approach to determine source mechanisms by minimizing the misfit error between corrected data and synthetics of SP P waves. The validation tests with calibration events demonstrate the importance and usefulness of the AAF corrections in recovering reliable results. We introduce the method with the 2003 Big Bear sequence. However, it applies equally well to other source regions in southern California, because we have shown that the mechanism independence and stability of the AAFs for source regions of 10 km by 10 km are typical. By definition, the AAFs contain the effects from the station site, the path, and crustal scattering. Although isolating their contributions proves difficult, the mechanism independence and stability of the AAFs suggest that they are mainly controlled by the near-receiver structure. Moreover, the ratios between the AAFs for the vertical and radial components from various events at different locations appear consistent, suggesting that these AAF(v)/AAF(r) ratios might be simple functions of site conditions. In this study, we obtained the focal mechanisms and moments for 92 Big Bear events with M L down to 2.0. The focal planes correlate well with the seismicity patterns, while containing abundant finer-scale fault complexity. We find a linear relationship between log(M 0 ) and M L , that is, log(M 0 ) ‫ס‬ 1.12M L ‫ם‬ 17.29, which explains all the data points spanning three orders of magnitude (2.0 Ͻ M L Ͻ 5.5).

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Section: Resultssupporting

confidence: 90%

A New Method for Determining Small Earthquake Source Parameters Using Short-Period P Waves

Tan¹,

Helmberger²

2007

Bulletin of the Seismological Society of America

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“…Other studies, where the majority of magnitudes are below 4, find similar values. For example, Archuleta et al (1982) find M L ∼ 1:56 0:1M w for 3 ≤ M L ≤ 6, in a study of source parameters for 40 earthquakes within a sequence of 1500 events at Mammoth Lakes, California; Kim et al (1989) find M L ∼ 1:49 0:05M w for earthquakes in the magnitude range of 2 ≤ M L ≤ 5:2, in a study of source parameters for earthquakes in the Baltic Shield. Many other studies find values between 1 and 1.9 over various magnitude ranges (see Deichmann [2006] and Hanks and Boore [1984] for a compilation).…”

Section: Summary and Discussionmentioning

confidence: 99%

Scaling Relations of Local Magnitude versus Moment Magnitude for Sequences of Similar Earthquakes in Switzerland

Bethmann

Deichmann

Martin

2011

Bulletin of the Seismological Society of America

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Theoretical considerations and empirical regressions show that, in the magnitude range between 3 and 5, local magnitude, M L , and moment magnitude, M w , scale 1∶1. Previous studies suggest that for smaller magnitudes this 1∶1 scaling breaks down. However, the scatter between M L and M w at small magnitudes is usually large and the resulting scaling relations are therefore uncertain. In an attempt to reduce these uncertainties, we first analyze the M L versus M w relation based on 195 events, induced by the stimulation of a geothermal reservoir below the city of Basel, Switzerland. Values of M L range from 0.7 to 3.4. From these data we derive a scaling of M L ∼ 1:5M w over the given magnitude range. We then compare peak Wood-Anderson amplitudes to the low-frequency plateau of the displacement spectra for six sequences of similar earthquakes in Switzerland in the range of 0:5 ≤ M L ≤ 4:1. Because effects due to the radiation pattern and to the propagation path between source and receiver are nearly identical at a particular station for all events in a given sequence, the scatter in the data is substantially reduced. Again we obtain a scaling equivalent to M L ∼ 1:5M w . Based on simulations using synthetic source time functions for different magnitudes and Q values estimated from spectral ratios between downhole and surface recordings, we conclude that the observed scaling can be explained by attenuation and scattering along the path. Other effects that could explain the observed magnitude scaling, such as a possible systematic increase of stress drop or rupture velocity with moment magnitude, are masked by attenuation along the path.

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“…For magnitudes in the interval 4-5, a nonlinear behavior of the moment-magnitude relation has been observed in several North American studies (e.g., Street et al, 1975;Hasegawa, 1983;Nuttli, 1986). A second-order regression based on the same data used by Kim et al (1989) together with the M w definition by Hanks and Kanamori (1979) gives…”

Section: Catalog Data: Mw Conversion and Spatiotemporal Completenessmentioning

confidence: 99%

“…The first set (a) is based on M w magnitudes converted from M L or from magnitudes compatible with M L . Kim et al (1989) derived a first-order relationship between seismic moment and M L (UPP) for earthquakes in the Fennoscandian shield in the magnitude range 2-5.1. However, their data contain only a few events with magnitude above 4.…”

Section: Catalog Data: Mw Conversion and Spatiotemporal Completenessmentioning

confidence: 99%

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

Wahlström

Grünthal

2001

Seismological Research Letters

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Regional spectral scaling relations of source parameters for earthquakes in the Baltic Shield

Cited by 26 publications

References 15 publications

A New Method for Determining Small Earthquake Source Parameters Using Short-Period P Waves

A New Method for Determining Small Earthquake Source Parameters Using Short-Period P Waves

Scaling Relations of Local Magnitude versus Moment Magnitude for Sequences of Similar Earthquakes in Switzerland

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

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