The M3+ EQs at 35.7 north are outside of my contest area and so the first M3 in what I consider Southern California has not occurred yet. See my contest rules in posts 15216, 15268, and 15287: has to be south of 35 N and in California or offshore US waters of the Borderland.
Here are the entries:
Canie revised her's when I gave that opportunity, done on 4/27: her's is 34deg 26.1' (34.435) and 116 12.7' (116.212) for 8 AM PDST April 29

Cathryn did not revise hers: her entry was posted 4/26 and was for 34.28N 118.43W. She gave a range of times and I only want a center time: so the range would be time of post on 4/26 to 4/30 PDT (midnight?). So, the center time would be on the 28th or maybe early on the 29th.

Lowell's is:
May 12 5:23 PDT
34.052N 118.376

Petra's was posted at 4/27 at 16:27:57. it is 33.24 M, -115.52 W. She gave a range from time of post to midnight on May 5. Since she did not correct that to a center time, I said that the midpoint of the time range would be the time: which is late on May 1, I think.

Lowell wondered whether Don's San Fernando prediction counted. It does not because:
It was not stated by Don that he was entering
The magnitude range he is predicting is mostly below M3, and for the contest the magnitude is defined as M3 or larger.
Adding him to the contest would have muddied his prediction.

For time, Lowell is now the only one that can be correct, but Petra would still be closest if it occurs in the next few days. For location-could be any of the 4 entries. For combined: I'm not sure how to do combined, but it may be obvious.
Chris