Why? What've you heard??
Depends on the speed & size of the comet, it's composition, and even the angle of impact... For large comets - I'm not sure there'd be *total* destruction, but more than just Los Angeles would be affected... It may wipe out most of the life on Earth.
There's a proposal that the "Great Flood" was caused by a comet impact in the Indian Ocean; it supposedly killed many people, and caused major weather patters to be disrupted. The legend of those changes has made it into several of the world's religions, but the damage/impact wasn't enough to wipe out mankind.
>>What would happen if a comet hit LosAngeles? Kilometer in diameter?
Guessing - for most comets with nuclei from 7 to 40 miles across - LA would be gone, as would most of the southwestern US. The effects would be felt worldwide.
At 35,000 mph, slush acts a lot like concrete... And, if there's a few *billion* tons... it's going to be very, very damaging.
>>It an undiscovered comet were to hit Los Angeles with little to no warning, what would happen?
The blast would likely be felt out to Utah or Colorado to the east, Oregon to the north, and down to Cabo Wabo in Baja...
>>How would things be on the east coast of the us?
Probably some in-falling debris, red hot and landing everywhere... followed by the smoke of the burning west-half of the US...
>>Would the power remain on on the east coast?
They're on the eastern power grid... Unless there were electrical/magnetic effects happening to our magnetic field... I *think* it would remain on.
>>How far from ground zero would power outages go?
Guessing... Portland, Colorado, Texas...
>>Would it cause an EMP? Pacific tsunami? Weather and climate effects?
I don't know why it would cause EMP... It's not an ionic mass hitting Earth, it's just a big snowball. A tsunami - maybe... probably not a major one if it hits on the shore, and none if it hits inland. Weather would be affected, depending on how much ocean was vaporized by the event.
>>Where would film and music industry be rebuilt?
I don't think we'd be worried about that for a while...
>>Possibly New Orleans or Austin? Maybe Atlanta?
Possibly any of those places; Atlanta already has a group of studios, I understand...
>>Would it spark a recession or depression in the rest of the us?
It would be a disaster. The government (assuming it survives) would be in an emergency mode. Probably most governments would be.
>>Would the comet’s ice spark a “comet winter” similar to the little ice age where there
>>were little frost fairs and such and would there be summer ice rinks and stuff and
>>would it go down in history is possibly the “Cold recession” which might be a
>>year or so of dim cold and snowy conditions where the economy is generally slow?
It may trigger impact winter, depending on it's size, with millions to billions starving to death in the following months.
>>How long till California is rebuilt?
>>Would it trigger earthquakes in San Fran and such? Possible wildfires? Would the
>>crater make a good harbor and would the new LA be built on the rim of the crater?
Quakes... possibly. Wild fires, at least for awhile. I doubt anyone except scientists and those with extreme curiosity would want to get close to the impact site for years. With no infrastructure, I bet that portion of California would revert back to desert.
>>How long till things in the economy go back to relatively normal?
Decades. And, it would be a "new normal."
>> How long will the “shaking” last?
Probably a few days, a few weeks, if it affects the faults at all.