The focal mechanism shows strike-slip. Strike-slip EQs less likely to make tsunami unless they trigger a large underwater slide. If they had known immediately that it was a M7 and that it was strike-slip, they probably did not need to issue a warning all up and down the California coast....but perhaps nearby was a reasonable precaution. But, there was probably a delay before they were confident in the magnitude, and a little longer before they had the focal mechanism...
Chris

• M7 quake