Local alliances and rivalries shape near-repeat terror activity of al-Qaeda, ISIS, and insurgents

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Significance

We examine near-repeat activity patterns of al-Qaeda, ISIS, and local insurgents, whereby a first terrorist attack temporarily increases the likelihood of a second one by the same group. We observe heightened near-repeat activity for all organizations in six geographic clusters and quantify the effect to persist within 20 km and 4 to 10 weeks after the first event. Near-reaction patterns, where two distinct groups react to each other’s activities, depend on the adversarial, neutral, or collaborative relationship between parties at the local level. We find no evidence of outbidding, whereas terrorist and state activities mutually reinforce one another. Our results may be useful for counterterrorism decision making and strategic resource allocation; near-repeat patterns may offer insight into local power structures.

Abstract

We study the spatiotemporal correlation of terrorist attacks by al-Qaeda, the Islamic State of Iraq and Syria (ISIS), and local insurgents, in six geographical areas identified via $k$ -means clustering applied to the Global Terrorism Database. All surveyed organizations exhibit near-repeat activity whereby a prior attack increases the likelihood of a subsequent one by the same group within 20 km and on average 4 (al-Qaeda) to 10 (ISIS) weeks. Near-response activity, whereby an attack by a given organization elicits further attacks from a different one, is found to depend on the adversarial, neutral, or collaborative relationship between the two. When in conflict, local insurgents respond quickly to attacks by global terror groups while global terror groups delay their responses to local insurgents, leading to an asymmetric dynamic. When neutral or allied, attacks by one group enhance the response likelihood of the other, regardless of hierarchy. These trends arise consistently in all clusters for which data are available. Government intervention and spillover effects are also discussed; we find no evidence of outbidding. Understanding the regional dynamics of terrorism may be greatly beneficial in policy making and intervention design.

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Dissipation and displacement of hotspots in reaction-diffusion models of crime.

P. Brantingham, A. L. Bertozzi, Martin B. Short … (2010)

The mechanisms driving the nucleation, spread, and dissipation of crime hotspots are poorly understood. As a consequence, the ability of law enforcement agencies to use mapped crime patterns to design crime prevention strategies is severely hampered. We also lack robust expectations about how different policing interventions should impact crime. Here we present a mathematical framework based on reaction-diffusion partial differential equations for studying the dynamics of crime hotspots. The system of equations is based on empirical evidence for how offenders move and mix with potential victims or targets. Analysis shows that crime hotspots form when the enhanced risk of repeat crimes diffuses locally, but not so far as to bind distant crime together. Crime hotspots may form as either supercritical or subcritical bifurcations, the latter the result of large spikes in crime that override linearly stable, uniform crime distributions. Our mathematical methods show that subcritical crime hotspots may be permanently eradicated with police suppression, whereas supercritical hotspots are displaced following a characteristic spatial pattern. Our results thus provide a mechanistic explanation for recent failures to observe crime displacement in experimental field tests of hotspot policing.