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A USC earthquake expert said his scientific advice was mostly disregarded by “San Andreas” movie filmmakers who asked him to review the script.

“I gave them free advice, some of which they took – play up ‘drop, cover, and hold on’ – but much of which they didn’t – magnitude 9’s are too big for the San Andreas, and it can’t produce a big tsunami,” said Thomas Jordan, USC professor and director of the Southern California Earthquake Center.

Jordan’s comments come after the film’s director, Brad Peyton, said in published reports that the film was based on science provided by Jordan, whom he called a consultant to the film, and that he “researched a lot” with Jordan.

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Jordan told the Los Angeles Times he was not a paid consultant, and that he agreed to read the script and met with the producer and director three times for free after being contacted through a National Academy of Sciences program that connects filmmakers with scientists.

Actor Dwayne Johnson, formerly known as The Rock, went a step further when he spoke on "The Tonight Show with Jimmy Fallon" last week.

“We had the world’s top seismologist and earthquake scientist pore over the script, challenge us with the script, so by the time they walked away they said, ‘Everything you guys shoot in the movie could actually happen,’ ” Johnson said. (The comment comes around after 1:50 in the clip below.)

“I certainly don’t agree with what Dwayne Johnson said on Jimmy Fallon the other night,” Jordan said.