The fact that the ground in Manhattan below 14th street is mud and
   honeycombed with building substructures as deep as the buildings are
   tall is NOT a "theory".
   Nor is the reason why the Harkins Slough flyway sank into the mud
   during the Loma Prieta Earthquake due to liquification a "Theory". My
   ex drove the pickup truck through it (the CHP was too busy to have set
   up roadblocks yet) on the way to pick me up after securing the kids and
   described the roadbed sitting almost at water level with the support
   columns NOT visible and sunk in the mud.
   I can't speak for the pancaking of the I-880 flyway in the Bay Area not
   knowing the geology of the land under it but you'd think an earthquake
   rocking it would toss it sideways. Especially considering the
   contractor building it had skimped on the reinforcing rebar. However
   the top deck collapsed directly on top of the deck below, killing and
   wounding a number of people. leading me to believe liquifaction was
   also involved. Much of the bay area is built on landfilled marshland.
   Rr