The economic impact of one-off terrorist attacks or man-made catastrophic events, is significant in the short-term, but inflicts very little long-term damage.
The economic system is highly resilient and adaptable, and can recover quickly. It should be born in mind that the economic system as it is managed today is prone to periodic crises anyway.
A one-time major terrorist attack more often causes a reallocation of resources rather than a loss of resources.
Because most terrorist attacks target the general public or government facilities instead of industrial centers, factories, ports, businesses, or supply chains; the economic impact is negligible.
At most, they create uncertainty, and negatively affect consumer activity. This tends to hurt small enterprises more than major businesses, and banks and insurance companies reap the benefits from this damage, while the bigger companies earn a larger market share as smaller competitors struggle to survive.
The main lesson here is that economic impact would be much greater if operations are carried out against “supply-side” targets, and if they are carried out in the form of smaller-scale but persistent attacks that cause ongoing disruption of operations, allowing no chance for recovery or adaptation.