Spatio-temporal extreme event modeling of terror insurgencies

TL;DR

This paper presents a novel spatio-temporal model for predicting terror attack occurrences and casualties, leveraging covariates and Gaussian Processes to improve understanding and forecasting of such extreme events.

Contribution

It introduces a self-exciting marked spatio-temporal model with a Gaussian Process prior for attack dependencies and a Generalized Zipf distribution for casualties, advancing terror event modeling.

Findings

Model accurately predicts attack intensities in Afghanistan from 2013-2018.

Incorporates covariates like population density and regional languages.

Effectively forecasts future attack risks for 2019-2021.

Abstract

Extreme events with potential deadly outcomes, such as those organized by terror groups, are highly unpredictable in nature and an imminent threat to society. In particular, quantifying the likelihood of a terror attack occurring in an arbitrary space-time region and its relative societal risk, would facilitate informed measures that would strengthen national security. This paper introduces a novel self-exciting marked spatio-temporal model for attacks whose inhomogeneous baseline intensity is written as a function of covariates. Its triggering intensity is succinctly modeled with a Gaussian Process prior distribution to flexibly capture intricate spatio-temporal dependencies between an arbitrary attack and previous terror events. By inferring the parameters of this model, we highlight specific space-time areas in which attacks are likely to occur. Furthermore, by measuring the outcome of an attack in terms of the number of casualties it produces, we introduce a novel mixture distribution for the number of casualties. This distribution flexibly handles low and high number of casualties and the discrete nature of the data through a {\it Generalized ZipF} distribution. We rely on a customized Markov chain Monte Carlo (MCMC) method to estimate the model parameters. We illustrate the methodology with data from the open source Global Terrorism Database (GTD) that correspond to attacks in Afghanistan from 2013-2018. We show that our model is able to predict the intensity of future attacks for 2019-2021 while considering various covariates of interest such as population density, number of regional languages spoken, and the density of population supporting the opposing government.