Reason Mag Q1 2014 Seite 31

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Figure 3 Cascadia margin turbidite canyons channels and sediment core locations Source Chris Goldfinger from Oregon State University A VIEW FROM ABOVEprehistoric data show The discrepancies can be attributed to ve reasons 1 The turbidite record may not be com plete at magnitudes less than 8 5 2 Some turbidite ows believed caused by magnitude 9 events might have been caused by multiple smaller events closely spaced in time 3 There could be substantial temporal variation in the earthquake rate at all magnitudes 4 The inferred magnitudes for the tur bidite earthquakes are subject to large uncertainties 5 The largest earthquakes in the Cascadia subduction zone might not follow the TGR distribution Additional studies are needed to determine which of the reasons are predominant What does it mean It s important to note that estimating prob able maximum magnitudes over differ ent time periods requires models and that any model must accept large uncertainties because of the limited earthquake data and reliance on proxy information In spite of the discrepancies between the TGR model and earthquake data at the middle magni tude range the TGR model illustrates that the subduction zone is expected to host magnitude 8 8 0 2 earthquakes within a 500 year period 9 0 0 2 events within a 1 000 year period and 9 3 0 2 events within a 10 000 year period The results can be veri ed by the turbidite data The USGS model is quite consistent with the turbidite data which is not surpris ing since the model is predominately based on turbidite data However the largest mag nitude considered in the USGS model is 9 2 with a small weight assigned to it Yufang Rong Ph D is a senior research scientist at FM Global O 1999 cores O 2002 cores O 1960s OSU cores O Primary 1999 cores PC O Additional archive cores Submarine canyons and channels 100 0 100 kilometers ISSUE 1 2014 Reason 31 theSCIENCE