| Possible triggering relationship of six M_w>6 earthquakes in 2018–2019 at Philippine archipelago |
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| 摘 要： | Philippine archipelago(PA) has strong background seismicity, but there is no systematic study of earthquake triggering in this region. There are six earthquakes(M_w 6) occurred between 2018/12/29 and 2019/09/29 in PA,which provides an excellent opportunity to investigate the triggering relationship among these events. We calculate the static Coulomb stress changes of the first five events, and find that the local seismicity after the2018/12/29 M_w 7.0 earthquake is mostly associated with positive Coulomb stress changes, including the2019/05/31 M_w 6.1 event, suggesting a possible triggering relationship. However, we cannot rule out the dynamic triggering mechanism, due to increased microseismicity in both positive and negative stress change regions, and an incomplete local catalog, especially right after the first M_w 7.0 mainshock. The dynamic stresses from these M_w 6 events are large enough(from 5 kPa to 3 532 kPa) to trigger subsequent events, but a lack of seismicity and waveform evidence does not support delayed dynamic triggering among these events, even the shortest time interval is less than 24 hours. In the past 45 years, the released seismic energy shows certain peaks every 5–10 years. However, earthquakes with M_w 6.0 were relatively infrequent between 2004 and 2018 at PA. Hence, it is possible that several regions are relatively late in their earthquake cycles, which would enhance their susceptibility of being triggered by earthquakes at nearby and regional distances.
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Possible triggering relationship of six Mw > 6 earthquakes in 2018–2019 at Philippine archipelago |
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| Authors: | Qiu Zhong Yangfan Deng Zhigang Peng Lingyuan Meng |
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| Abstract: | Philippine archipelago (PA) has strong background seismicity, but there is no systematic study of earthquake triggering in this region. There are six earthquakes (Mw > 6) occurred between 2018/12/29 and 2019/09/29 in PA, which provides an excellent opportunity to investigate the triggering relationship among these events. We calculate the static Coulomb stress changes of the first five events, and find that the local seismicity after the 2018/12/29 Mw 7.0 earthquake is mostly associated with positive Coulomb stress changes, including the 2019/05/31 Mw 6.1 event, suggesting a possible triggering relationship. However, we cannot rule out the dynamic triggering mechanism, due to increased microseismicity in both positive and negative stress change regions, and an incomplete local catalog, especially right after the first Mw 7.0 mainshock. The dynamic stresses from these Mw > 6 events are large enough (from 5 kPa to 3532 kPa) to trigger subsequent events, but a lack of seismicity and waveform evidence does not support delayed dynamic triggering among these events, even the shortest time interval is less than 24 hours. In the past 45 years, the released seismic energy shows certain peaks every 5–10 years. However, earthquakes with Mw > 6.0 were relatively infrequent between 2004 and 2018 at PA. Hence, it is possible that several regions are relatively late in their earthquake cycles, which would enhance their susceptibility of being triggered by earthquakes at nearby and regional distances. |
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| Keywords: | static triggering dynamic triggering seismicity ETAS model Philippine archipelago |
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