Comment on "Late Holocene Rupture of the Northern San Andreas Fault and Possible Stress Linkage to the Cascadia Subduction Zone" by Chris Goldfinger, Kelly Grijalva, Roland Burgmann, Ann E. Morey, Joel E. Johnson, C. Hans Nelson, Julia Gutierrez-Pastor, Andrew Ericsson, Eugene Karabanov, Jason D. Chaytor, Jason Patton, and Eulalia Gracia

Abstract

Goldfinger et al. (2008) conclude that in the northern San Andreas fault and Cascadia margins, Holocene turbidites (i.e., deposits of turbidity currents) were triggered by earthquakes. However, their conclusion falters because of (1) selective data sets that were used for establishing seismicity as the sole triggering mechanism of turbidites, (2) flawed sedimentological concepts and criteria that were applied for interpreting turbidites, and (3) faulty methodologies that were employed for correlating turbidites over long distances. This same turbidite (i.e., sedimentological) theme has also been published previously by Goldfinger et al. (2003a,b, 2006, 2007). As with the recent article in BSSA , their previous publications on the subject matter were published in journals that are concerned primarily with geophysical topics. As a result, critical sedimentological conclusions, which are an integral part of the articles by Goldfinger et al. , have not been subjected to a rigorous scrutiny. Therefore, I would like to comment on the following three issues. Along the Washington–Oregon–California margin, potential triggering mechanisms of sediment failures and related turbidity currents are (1) earthquake (Adams, 1990), (2) tectonic oversteepening (Greene et al. , 2006), (3) tsunami (Adams, 1990; Geist, 2005), (4) cyclone (Adams, 1990; Shanmugam, 2008a, fig. 4), (5) ebb tidal current (Puig et al. , 2003), (6) submarine volcanic activity (Davis et al. , 2002), (7) sediment loading (Adams, 1990), and (8) gas hydrates (Chapman et al. , 2004). The link between gas-hydrate decomposition and mass movements on the Norwegian margin was discussed by Mienert et al. (2005). In the Cascadia margin, a total of 40 cyclones along the Oregon coast were reported for the 1984–2006 period (Moritz and Moritz, 2006). A total of 24 tsunamis were reported along the Oregon coast for the 1868–1994 period (Table 1). Cyclones and tsunamis are powerful agents of sediment failures (Shanmugam, 2008a). On the outer continental shelf of the Gulf of Mexico, for example, the …