Additional file 1 of Reappraisal of volcanic seismicity at the Kirishima volcano using machine learning
Creators: name: Yukutake, Yohei
name: Kim, Ahyi
name: Ohminato, Takao
Publisher: name: figshare
Year: 2024
Subjects: subject: Geology
subject: FOS: Earth and related environmental sciences
subject: Geophysics
subject: Artificial Intelligence and Image Processing
subject: FOS: Computer and information sciences

description: Additional file 1: Figure S1. Estimated 1D velocity model and station corrections. (a) 1D velocity model for P- and S-waves; the Vp/Vs structure is shown on the right. The dotted lines represent the initial velocity, and the solid lines represent the velocity model modified by the JHD method. (b) Station (travel time) corrections for the P-waves (left) and S-waves (right). Circles show positive travel time residuals (i.e., an observed travel time is later than a theoretical one), while crosses show negative travel time residuals. Figure S2. Comparison of frequency distribution of the travel time residuals between the initial hypocenters ((a) and (b)) and the relocated hypocenter ((c) and (d)) by applying the modified 1D velocity model and station corrections. Figure S3. Temporal changes in b-values and Mc as estimated using the maximum curvature method. The horizontal and vertical lines at each point show the time window for selecting the earthquakes and the error bar of the b-value (top panel) or Mc (bottom panel) as estimated using the bootstrap resampling method. The color spectrum in the bottom figure shows the delta M value or magnitude bandwidth equal to the largest magnitude minus Mc in each time window. Please note that the seismic catalog is not split before and after the eruption occurrence time. Figure S4. Temporal changes in b-values and Mc values as estimated by the goodness-of-fit test. Figure S5. Temporal changes in b-values and Mc values estimated using the b-value stability method. Figure S6. Hypocenter distribution of the earthquake beneath the Kirishima volcano in the JMA catalog. The top panel shows the epicentral distribution, and the top-right and bottom panels indicate the depth distribution along the N–S and E–W sections, respectively. The depth of 0 km corresponds to the sea level. Figure S7. Depth–time distribution and cumulative number of earthquakes in the JMA catalog. The blue lines indicate the cumulative curve containing volcano tectonic and low-frequency earthquakes. The black circles indicate the depth–time plot of the earthquakes. The dotted vertical yellow lines show the occurrence times of the main events: the 2011 Shinmoedake eruption, the 2016 Kumamoto earthquake, the 2017 and 2018 Shinmoedake eruptions, and the 2018 Iwo-yama phreatic eruption. (a) Whole region, (b) Shinmoedake, and (c) Iwo-Yama. The regions of Shinmoedake and Iwo-Yama correspond to the maps shown in Figures 3a and 3b, respectively. Figure S8. Comparison of magnitude–frequency distribution between two seismic catalogs: (a) ML and (b) JMA. Squares represent cumulative magnitude–frequency distribution; triangles represent the number of events in each magnitude bin; blue inverted triangles represent Mc; and red lines represent linear regressions for both catalogs. Figure S9. Comparison of the amplitude spectra of the seismograms of A-type (blue line) and B-type (red line) earthquakes based on the JMA catalog. The light blue and red lines show several examples of spectrograms of B- and A-type earthquakes, respectively. The dark blue and red lines show the stacked spectrograms. (a) EV. KVO and (b) EV. EBS stations. Figure S10. (a) and (b) shows frequency distribution of FI values obtained at (a) EV. KOV and (b) EV. EBS stations. We estimated the median of FI values at each station and subtracted it from the estimated FI values. (c) Frequency distribution of the standard deviation for the final FI values after applying the station correction Figure S11. Relationship between FI and magnitude: (a) JMA catalog and (b) ML catalog. (c) and (d) show examples of waveform records in the EW component at EV. KAR station. (c) and (d) correspond to the waveforms of low-frequency and volcano-tectonic earthquakes in ML catalog classified based on the FI value, respectively. The text at the top of (c) and (d) indicates the origin time, latitude, longitude, depth, magnitude, and FI value of the earthquake. Figure S12. Hypocenter distribution, depth–time distribution, and cumulative number of earthquakes during 2016–2019 detected using Model 4 by Kim et al. (2023). Hypocenters were relocated using the DD method. Figure S13. Comparison of cumulative numbers of earthquake between JMA (blue line) and ML (red line) catalogs. (a) Whole region, (b) Shinmoedake, and (c) Iwo-Yama. The regions of Shinmoedake and Iwo-Yama correspond to the maps shown in Figures 3a and 3b, respectively. Figure S14. Examples of waveform records of vertical motion, showing manually picked (solid line) and automatically (broken line) picked arrival times. The red and blue lines show the onset times of the P and S waves, respectively. The text in the upper portion of each panel indicates the origin time and magnitude. Figure S15. Comparison of the initial hypocenters before the DD relocation and their temporal seismicity sequence during 2017–2019: (a) learning model derived from volcanic earthquakes (Kim et al., 2023) and (b) original learning model by Zhu and Beroza (2018). The dotted vertical yellow lines in each bottom panel show the occurrence time of the main events, as shown in Figure S4. Figure S16. Histograms showing the frequency distribution of magnitude for earthquakes detected by the model trained on the volcanic earthquake catalog (Kim et al. 2023) from 2017 to 2019. (Left) Blue bins constitute a histogram for all events; red bins constitute a histogram for only those events detected by the trained model of Kim et al. (2023) (Model 1). (Right) Red bins constitute a histogram for only those events detected by the trained model of Zhu and Beroza (2019). Figure S17. Example of Magnitude–frequency distribution of earthquakes beneath Shinmoedake for two periods: (left) March 1, 2016– July 24, 2016 (right) January 2, 2018–February 27, 2018. Each panel contains 300 events, which is the same number of events used to estimate the temporal distribution of b-value in Figure 4 of the main text. Red line represent linear regressions.