Literally crushing San Francisco

Hi, I'm writing a sci fi novel where at the end of the second act, north-central San Francisco is crushed by a space ship about less than a third the cities size and the details of how the city could be crushed don't seem to exist on the internet... and neither does the proper information to allow me to piece together some information myself, so I came here.

The resources that I found pointed at X-Men 3, The Core, and oddly enough for the level of destruction that I am seeking, Star Trek IV. Only highlighting the destruction the Golden Gate Bridge does not help me.

This ship in my story has a stable hover from about three quarters of a mile up from sea level before it fails. On top of that, a 3,000 foot wide energy blast had ripped through from about the Fort Mason Center to Thorton State Beach, causing the ocean to fill in that new canal shortly before the ship crushes the city. That's probably a four mile expanse.

I'm not worrying about human death since the city was evacuated beforehand. I know that the sewer system is fairly old and that the buildings are depending on its now delicate structure, but that doesn't help me much.

In short, how can I literally crush the city of San Francisco after it got a horrid ocean filling scar going through it, and make it realistic? Since the rest of the internet was of little help.

Thanks tropers for assisting me in my horrible request. My Google-fu kinda failed me. I'll be glad to answer any questions regarding details that I could have left out... or to address my vagueness.

It's a giant spaceship made of who-knows-what impacting an area that was already destabilized by a giant energy beam slicing through the ground. Seems fairly straightforward, really; given the sci-fi trappings, nobody's going to be able to call BS on this.

The real question is why you want such a level of detail. Through whose eyes do we see the disaster happen? If it is through an omniscient, disembodied third-person narrator, then the scene runs the risk of falling flat. Since the city is evacuated, we cannot fear for its inhabitants; all we are seeing, in the end, is inanimate objects falling down. But it's hard to have a strong emotional attachment to inanimate objects. Movies can sometimes get away with things like that if the special effects make it look cool enough, but writing doesn't have that easy way out.

Seen through someone's eyes, however, this could be fascinating. How does that character react to what they are seeing? Are they awed by the sheer scope of the collapse occurring before their eyes? Depending on their role in the proceedings, are they satisfied? Horrified? Guilty? Scared? Do they feel loss, or triumph, or relief that they escaped unscathed? The human element is the real meat of the story. Of course, this makes the question of the exact process by which this occurs far less relevant. The character doesn't have an omniscient knowledge of the exact processes by which the shockwaves caused by the spaceship's impact caused the already unstable ground to begin to shift beneath the surface which leads to blah blah blah; what the character knows is that a giant spaceship fell and buildings started breaking apart and collapsing.

But that's good! A technical analysis of the precise means by which the city collapses will not be terribly interesting to the reader, especially since the science fiction premise ensures that almost anything you write down will be "realistic". It's human reaction and emotion that will make or break the scene, not precise details of tectonic activity that the characters won't even notice.

I ask for such a level of detail (well, accuracy really) because disasters come in different flavors. The Mount St Helens eruption was vastly different from Hurricane Katrina was vastly different from, well, the 1906 destruction of San Francisco. A deeper reasoning would be that one does not expect a brick wall to be torn down by an aluminum bat, nor can anyone expect Steve's fist to mine through rock to make a cave with quick results. San Fransisco is a delicate city on top of a bunch of hills. It's easy to say that the city was crushed with a new canyon running through, but how would that affect the bay, or the airport, or the geographical outlaying areas?

To be more concise, I was looking for whether the weight of the ship would crush the city to sea level, or whether the new canyon would make the hills collapse and cause a crater because of the ship, or if it would be stable enough? I'm keeping (in-universe eventual) city wide rehabilitation in mind for the city too. How important is San Fransisco as a city, and how stubborn is the human race to not erect a new thing to celebrate the old?

As for emotions from the characters? I've got nothing beyond making it feel (not be) similar to the fall of the Hometree in Avatar. My super heroes neither succeeding nor failing, but forced with a third option presenting both outcomes in a terrible way.

Watch this: the buildings that the spaceship lands on buckle and collapse under it because they're just normal buildings and it's a giant spaceship. The ground was previously destabilized by the cuts made by the energy beams, and this impact is enough to make the ground start sliding into the hole formed. Between the shockwaves from the impact and the earth moving downward, the rest of the buildings just fall as the ground beneath them shakes and slides away. Rebuilding is impractical because the ground itself is too unstable for a strong foundation so nobody wants to build there.

But really, that's not the main thing I'd be focusing on if I were you. No geologist is going to crawl out of the woodwork to argue with you about what would REALLY happen if a giant spaceship were to fall on an empty city whose ground had been previously devastated by energy beams slicing new canyons into the earth. The exact details there really aren't all that important. The character emotions are the real meat that actually make stories worth reading, and if your first response on that topic is "I've got nothing", then that's definitely where you'd be best advised to focus your efforts. Readers don't care about the precise geological processes of the big explosions - they care about people.

Any spaceship sufficiently large to crush a large portion of the city may not have to land to accomplish this. If you're picturing something like the size of the ID 4 ships, they'd actually crush the city via air pressure buildup beneath them.