10:45 〜 11:00
[J02-2-02] The 2016 Mw 7.8 Pedernales, Ecuador earthquake: aftershock sequence analysis using a minimum 1D velocity model
On the 16th April 2016, a Mw 7.8 mega-thrust earthquake occurred in northern Ecuador, close to the city of Pedernales. The event ruptured an area of 120 x 60 km and was preceded by a Mw 4.8 foreshock, located only ~15 km south of the epicentre, and registered 10 minutes before the main event.
A few weeks after the main event a large array of instruments was deployed by a collaborative project between the Geophysical Institute of Ecuador (IGEPN), IRIS (USA), Geoazur (France) and the University of Liverpool (UK). This dense seismic network, with more than 70 stations, includes broadband, short period, strong motion and OBS instruments and is currently recording the aftershock activity of the main event.
Using data recorded both on the permanent and the recently deployed network we manually picked -with SDX- and located -with SDX and NonLinLoc- 250+ events corresponding to the aftershock sequence. P and S arrival times were used to obtain a minimum 1D velocity model. After relocate the seismicity we analysed the spatial distribution and its relation with the co-seismic slip and with previous models of inter-seismic coupling. It is possible to identify two lineations in the aftershock activity located to the north and south of the rupture. Moreover, the geodetic slip model shows that the boundaries of the maximum coseismic slip coincides with the observed lineaments in the aftershocks and with the rupture area of a previous Mw 7.8 event in 1942. This suggests that the features to the north and south may impose a barrier to rupture propagation, creating different segments in the subduction zone beneath Ecuador.
Previous activity has presented a northward-propagating series of ruptures greater than Mw 7 spaced approximately 20 years apart. An open question is therefore whether the present event is the start of a further series of large magnitude events in northern Ecuador, and whether slow slip events/creep in the south have fully accommodated the strain due to subduction.
A few weeks after the main event a large array of instruments was deployed by a collaborative project between the Geophysical Institute of Ecuador (IGEPN), IRIS (USA), Geoazur (France) and the University of Liverpool (UK). This dense seismic network, with more than 70 stations, includes broadband, short period, strong motion and OBS instruments and is currently recording the aftershock activity of the main event.
Using data recorded both on the permanent and the recently deployed network we manually picked -with SDX- and located -with SDX and NonLinLoc- 250+ events corresponding to the aftershock sequence. P and S arrival times were used to obtain a minimum 1D velocity model. After relocate the seismicity we analysed the spatial distribution and its relation with the co-seismic slip and with previous models of inter-seismic coupling. It is possible to identify two lineations in the aftershock activity located to the north and south of the rupture. Moreover, the geodetic slip model shows that the boundaries of the maximum coseismic slip coincides with the observed lineaments in the aftershocks and with the rupture area of a previous Mw 7.8 event in 1942. This suggests that the features to the north and south may impose a barrier to rupture propagation, creating different segments in the subduction zone beneath Ecuador.
Previous activity has presented a northward-propagating series of ruptures greater than Mw 7 spaced approximately 20 years apart. An open question is therefore whether the present event is the start of a further series of large magnitude events in northern Ecuador, and whether slow slip events/creep in the south have fully accommodated the strain due to subduction.