Group B, Poster #064, Seismology
A new look into the 2004 M6 Parkfield Earthquake sequence using an updated earthquake catalog
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Poster Presentation
2022 SCEC Annual Meeting, Poster #064, SCEC Contribution #12556 VIEW PDF
between the detections and templates with a principal component fit.
Analysis of seismicity rate changes before the 2004 mainshock does not show clear precursory signals, although we find a change in the seismic activity in the creeping section of the San Andreas Fault (about ~25 km NW of the mainshock epicenter) in the weeks prior to the mainshock. We also observe a decrease in the b-value parameter in the Gutenberg-Richter relationship based on the b-positive estimate (van der Elst, 2021) in the creeping section in the months prior to the mainshock. However, no clear changes in the b-value and seismicity rate are found in the Parkfield section where the 2004 mainshock ruptured.
Additionally, we use the new catalog to study interactions between tidal stresses and afterslip with seismicity during the 2004 earthquake sequence. We find that seismicity before the mainshock is modulated by fortnightly tides and by semi-diurnal tides modulate only during the falling fortnightly tide. In contrast we find a significant semi-diurnal modulation of aftershocks at all periods. Preliminary results combining our PKD-MR catalog with the observations of afterslip evolution by Jiang et al. (2021) and the afterslip-driven aftershock model of Perfettini et al. (2018), show that the observed up- and down-dip and along-strike expansion of early aftershocks are well explained by afterslip evolution.
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Analysis of seismicity rate changes before the 2004 mainshock does not show clear precursory signals, although we find a change in the seismic activity in the creeping section of the San Andreas Fault (about ~25 km NW of the mainshock epicenter) in the weeks prior to the mainshock. We also observe a decrease in the b-value parameter in the Gutenberg-Richter relationship based on the b-positive estimate (van der Elst, 2021) in the creeping section in the months prior to the mainshock. However, no clear changes in the b-value and seismicity rate are found in the Parkfield section where the 2004 mainshock ruptured.
Additionally, we use the new catalog to study interactions between tidal stresses and afterslip with seismicity during the 2004 earthquake sequence. We find that seismicity before the mainshock is modulated by fortnightly tides and by semi-diurnal tides modulate only during the falling fortnightly tide. In contrast we find a significant semi-diurnal modulation of aftershocks at all periods. Preliminary results combining our PKD-MR catalog with the observations of afterslip evolution by Jiang et al. (2021) and the afterslip-driven aftershock model of Perfettini et al. (2018), show that the observed up- and down-dip and along-strike expansion of early aftershocks are well explained by afterslip evolution.
SHOW MORE