Abstract
The 2016 Ecuador MW7.8 earthquake ruptured the subduction zone boundary between the Nazca and South American plates. Joint modeling of seismic and tsunami observations indicates an ∼120 km long rupture area beneath the coastline north of the 1998 MW7.2 rupture. The slip distribution reveals two discrete asperities near the hypocenter and around the equator. Their locations and the patchy pattern are consistent with the prior interseismic geodetic strain, which showed highly locked patches also beneath the coastline. Aftershocks cluster along two streaks, one aligned nearly parallel to the plate convergence direction up-dip of the main slip patches, and the other on a trench-perpendicular lineation south of the 1958 rupture zone. Comparisons of seismic waveforms and magnitudes show that the 2016 event and 1942 earthquakes have similar surface wave magnitude (MS7.5), overlapping rupture areas, and similar main pulses of moment rate. The same area ruptured as the southernmost portion of the larger earthquake of 1906 (MW8.6, MS8.6). The seismic behavior reflects persistent heterogeneous frictional properties of the Colombia–Ecuador megathrust.
| Original language | English |
|---|---|
| Pages (from-to) | 248-258 |
| Number of pages | 11 |
| Journal | Earth and Planetary Science Letters |
| Volume | 454 |
| DOIs | |
| Publication status | Published (in print/issue) - 15 Nov 2016 |
Funding
The IRIS DMS data center ( http://www.iris.edu/hq/ ) was used to access the seismic data from Global Seismic Network and Federation of Digital Seismic Network stations. Bernard Dost at the Royal Netherlands Meteorological Institute in Dutch helped check the peak-to-peak amplitude and the instrumental response for the 1942 event, and also provide the broadband record for the 2016 event at Debilt. Björn Lund at Uppsala university helped check the historical instrumental responses at Uppsala station. Omori seismograms for the 1906 earthquake are provided by the Mizusawa observatory. Stephen Hartzell and Tom Heaton provided high-resolution copies of Pasadena P waveforms records for the 1942, 1958 and 1979 events. The copies of the papers of the Gutenberg notepad are provided by the Archives of the California Institute of Technology. James Dewey at USGS provided us ISC-NEIC information on M S for 1979 and 2016 events. Stephen Hernandez helped provide access to the local seismic catalog. Mohamed Chlieh provided his preferred geodetic coupling model. Yong Wei provided the post-processed DART and tide gauge time series, where the original data can be downloaded from the NOAA National Data Buoy Center ( http://www.ndbc.noaa.gov/ ) and CO-OPS Tsunami Capable Tide Stations ( http://tidesandcurrents.noaa.gov/tsunami/ ). David Sandwell and Xiaohui Xu at UC San Diego, Karsten Spaans and Andrew Hooper at Leeds showed us their InSAR images respectively for comparison, along with helpful discussions. This data analysis made use of GMT, SAC, and Matlab software. We thank Nadia Lapusta and Luis Rivera for helpful discussion. This work was supported by NSF grant EAR1245717 to Thorne Lay, and Caltech Seismological Laboratory Director's fellowship to Lingling Ye.
Keywords
- 2016 Ecuador earthquake
- Ecuador–Colombia earthquake sequence
- re-rupture of 1942 event
- source rupture model