B-Positive for Induced Seismicity Catalogs With Time-Varying Incompleteness? Proceed With Caution.
Description:
The relative frequency of large versus small earthquakes is characterized by the b-value of the earthquake magnitude-frequency distribution. The b-positive method, recently introduced by Van der Elst (2021) to estimate the b-value in transient incomplete catalogs, is based on the Laplacian distribution of magnitude differences. The method was developed to handle time-varying incompleteness in aftershock sequences and was found to be much more robust to unknown or variable incompleteness due to network limitations. However, the method still requires some minimum cutoff value M’c above which the b-value can be accurately derived.
More recently, the method has also been applied to induced seismicity sequences with time-varying incompleteness in the catalogs. These assessments generally adopt small minimum cutoff values, similar to the values presented for aftershock sequences. The results show significantly different time-variations in b compared to the traditional Gutenberg-Richter exponential maximum likelihood estimates. However, turns out these low cutoff values lead to significant underestimations of the actual b-values. Closer analysis on synthetic catalogs shows that a significant trade-off exists between the minimum value M’c and the magnitude range over which incompleteness occurs, the scale parameter σ describing how quickly 100% detection is achieved. As time-varying incompleteness may also imply time-varying σ, the implication for the interpretation of time-varying b-values is very significant. Analysis of the Groningen induced seismicity catalog demonstrates this further. As the b-value is one of the critical parameters controlling seismic hazard and risk, the b-positive estimate should thus be handled with due care.
Session: Seismic Monitoring, Modelling and Management Needed for Geothermal Energy and Geologic Carbon Storage - III
Type: Oral
Date: 5/2/2024
Presentation Time: 02:15 PM (local time)
Presenting Author: Annemarie
Student Presenter: No
Invited Presentation:
Authors
Annemarie Muntendam-Bos Presenting Author Corresponding Author a.g.muntendam-bos@tudelft.nl Delft University of Technology |
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B-Positive for Induced Seismicity Catalogs With Time-Varying Incompleteness? Proceed With Caution.
Session
Seismic Monitoring, Modelling and Management Needed for Geothermal Energy and Geologic Carbon Storage