Petra, the fault system was know earlier. There is a paper by Yeats et al 1994 AAPG Bulletin with a bunch of cross sections, and the industry-related Ventura Basin Study group had subsurface structure-contour maps and cross sections (see link), and I think Dibblee had Geologic maps and cross sections out by then. The Northridge EQ was on a "blind" fault, which loosely means that the fault is buried and its deep slip is transformed into folding. The folds have been known in the subsurface for probably 80 years-maybe more.....

research published in 1993 showed GPS results of how rapidly Ventura basin is getting sqeezed shut (e.g., Donnellan et al., 1993 JGR).

Chris

• cross sections and maps