Question

question 13 (0.71 points)
us geological survey scientists monitoring the earthquake-prone parkfield, ca region noticed _______________ prior to the 2004 earthquake.
all of these
no significant precursors
changes in magnetic field
a very significant foreshock
changes in shear (rock deformation)

Explanation:

USGS monitoring of Parkfield, CA before the 2004 earthquake found no clear, reliable significant precursors. The proposed changes in magnetic field, shear deformation, or a major foreshock were not observed as consistent, predictive signals for this event.

Answer:

no significant precursors