Figure 2. Source properties of the doublet. (a) Moment-rate sequence: the magnitude 7.2 foreshock lasted about 23 seconds. 39 seconds after it began, the magnitude 7.5 mainshock struck. The two events were separated by an approximately 15-second pause in moment release, the signature of a stress-triggered pair rather than one continuous rupture; the beachballs show that both events share the same near-vertical, east–west, right-lateral (San Sebastián) mechanism. (b) Magnitude-duration scaling of shallow (less than 30 kilometer) global earthquakes (2016–2026): Because the mainshock’s automatic source-time function was not resolved, its duration is estimated from this scaling at about 35 seconds (range of about 27–45 seconds). Source durations from USGS NEIC W-phase solutions; full finite-fault analysis of the doublet is ongoing. Credit: Chaves et al., 2026, CC BY-NC-ND 4.0

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Figure 2. Source properties of the doublet. (a) Moment-rate sequence: the magnitude 7.2 foreshock lasted about 23 seconds. 39 seconds after it began, the magnitude 7.5 mainshock struck. The two events were separated by an approximately 15-second pause in moment release, the signature of a stress-triggered pair rather than one continuous rupture; the beachballs show that both events share the same near-vertical, east–west, right-lateral (San Sebastián) mechanism. (b) Magnitude-duration scaling of shallow (less than 30 kilometer) global earthquakes (2016–2026): Because the mainshock’s automatic source-time function was not resolved, its duration is estimated from this scaling at about 35 seconds (range of about 27–45 seconds). Source durations from USGS NEIC W-phase solutions; full finite-fault analysis of the doublet is ongoing. Credit: Chaves et al., 2026, CC BY-NC-ND 4.0

Figure 2. Source properties of the doublet. (a) Moment-rate sequence: the magnitude 7.2 foreshock lasted about 23 seconds. 39 seconds after it began, the magnitude 7.5 mainshock struck. The two events were separated by an approximately 15-second pause in moment release, the signature of a stress-triggered pair rather than one continuous rupture; the beachballs show that both events share the same near-vertical, east–west, right-lateral (San Sebastián) mechanism. (b) Magnitude-duration scaling of shallow (less than 30 kilometer) global earthquakes (2016–2026): Because the mainshock’s automatic source-time function was not resolved, its duration is estimated from this scaling at about 35 seconds (range of about 27–45 seconds). Source durations from USGS NEIC W-phase solutions; full finite-fault analysis of the doublet is ongoing. Credit: Chaves et al., 2026, CC BY-NC-ND 4.0

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