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Fig. 1 | Earth, Planets and Space

Fig. 1

From: Efficiency of earthquake forecast models based on earth tidal correlation with background seismicity along the Tonga–Kermadec trench

Fig. 1

Interplate (thrust) earthquakes (focal depth ≤ 70 km, Mw ≥ 5.5) that occurred along the Tonga–Kermadec trench during the period 1 January 1977 to 31 December 2020 (N = 729). a Epicenter distribution. The purple lines denote plate boundaries at Earth’s surface (Bird 2003). Colored, dashed contours indicate the depth (km) to the upper surface of the subducting Pacific slab (Hayes 2018). White and black arrows indicate the movement of the Pacific plate relative to the Tonga plate (TO) and Kermadec plate (KE), respectively. b Time–space plot of earthquakes. c Time-series plot of earthquake magnitudes (red bars indicate events with Mw ≥ 7.0) and the cumulative number of earthquakes (black trend). Events with letters * and + indicate events excluded from the forecast target because of insufficient data to calculate a p-value. Events with letters A to J indicate the forecast targets. These events with letters correspond to red circles in d. d Relation between phase angle and tidal normal stress on the fault at the time of earthquake occurrence; red symbols indicate events with Mw ≥ 7.0. (e) Frequency distribution of tidal phase angles estimated using the normal stress Δσ on the fault. The estimated p-value (Eq. 1) is shown at top-right. The dashed horizontal line indicates the mean frequency (100%/18 bins)

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