I spoke with Kennedy about his progress, and the challenges of simulating the aftermath of a disaster in one of the world’s biggest cities. A transcript of our conversation, lightly edited for concision and clarity, follows.

Waddell: How will your computer model be able to accurately simulate people’s responses?

Kennedy: First, we’re doing basic research to try and identify how we expect people to respond, and how the environment and infrastructure and facilities would respond. When we get verbal descriptions that we are comfortable with, we will represent them more precisely as computer programs. We’ll start with the environment, the weapon and its effects, and then move on to the people, the infrastructure, and their response.

We’ve done other models of similar-sized areas, modeling natural disasters and things like that. So we have some infrastructure to support us. We’re using the MASON framework: It’s open source—our computer-science department distributes it and maintains it—and we’ve used it in several projects here.

We’ll be bringing in graphical information on New York City and surrounding area, and we’ll model a small nuclear weapon—or possibly multiple small nuclear weapons—going off. They’ll be in the neighborhood of 5 to 10 kilotons: That’s half of Nagasaki/Hiroshima, which was in the 20 kiloton range. The Oklahoma City bomber used 5,000 pounds of TNT, so that’s two and a half tons. That destroyed most of the one building where it blew up, but it affected something like 16 city blocks.

Waddell: So we’re talking damage to something like a chunk of Manhattan?

Kennedy: Yes, something like that. The number 10 isn’t driven by any particular intelligence, but to put it into perspective, North Korea has done tests in the neighborhood of two kilotons—or maybe as many as five. So we’re talking a relatively small, though still nuclear, weapon.

Waddell: What are the social responses you’ll look at?

Kennedy: We’re planning to model at the individual level. A megacity is more than 10 million, and in the region we’re talking about, we’ll potentially get to 20 million agents.

We’ve found that people seem to be reasonably well behaved and do what they’ve been trained to, or are asked or told to do by local authorities. Reports from 9/11 show that people walked down many tens of flights of stairs, relatively quietly, sometimes carrying each other, to escape buildings.

We’re finding those kinds of reports from other disasters as well—except after Hurricane Katrina. There, we have reports that people already didn’t trust the government, and then with the isolation resulting from the flooding, they were actually shooting at people trying to help.

Waddell: So is the difference between the two disasters trust and communication?

Kennedy: I suspect that’s a large part of it, yes.