Seat of Blast
Definition
The precise point of initiation of the detonation, identified from the convergence of crater geometry, witness-mark vectors, damage gradient, and residue concentration.
- Definition
- Precise point of detonation initiation
- Evidence used
- Crater geometry, witness-mark vectors, damage gradient, residue
- Method
- Convergence analysis of multiple indicators
- Field
- Post-blast scene investigation
Common questions
Why is a crater alone not enough to fix the seat of blast?+
A crater confirms roughly where a device functioned but not always its exact centre, especially on hard or angled surfaces, so investigators cross-check the crater against fragment throw direction, structural damage severity radiating outward, and residue concentration to converge on a single point rather than relying on the crater's shape alone.
How do witness-mark vectors help locate the seat of blast?+
Fragments and shockwave effects leave directional scarring, spalling, and pitting on nearby surfaces that point back toward their origin, and plotting several of these vectors from different surfaces lets investigators triangulate the seat even when the crater itself is obscured or absent.
Why does explosive residue concentration peak near the seat of blast?+
Unconsumed or partially reacted explosive material tends to be thrown shortest distances and deposits most heavily close to the point of initiation, so a residue concentration gradient that decreases with distance from a candidate location supports that location as the true seat.
Related terms
- Crater Glass
- Glass fragments recovered from within or immediately adjacent to the blast crater, originating from the device container or adjacent glazing; distinguished by...
- Expanding Concentric Search Grid
- The systematic spatial framework for post-blast scene searches, consisting of concentric rings at measured radii from the seat of blast, divided into...
- Ion Mobility Spectrometry (IMS)
- A field-deployable analytical technique that separates ions by their mobility in an electric field at atmospheric pressure. Used for trace explosive detection...
- JESIP
- Joint Emergency Services Interoperability Programme (UK); the framework mandating co-located multi-agency command with a shared decision log from initial response, applied to...
- Paint Transfer Analysis
- Forensic comparison of paint layer sequences (primer, base coat, lacquer) on near-field surfaces against reference samples to identify the vehicle or container...
- Render-Safe Procedure
- The action taken by a qualified EOD or bomb disposal team to make a blast scene or live device safe from secondary...
- Scene Log
- The contemporaneous record of every person entering and exiting the inner cordon, with time stamps and roles; the foundational chain-of-custody document for...
- Sieve Recovery
- The process of collecting and dry- or wet-sieving soil and debris from the crater and innermost grid zone through 2 mm and...
- Witness Mark
- A fragment embedded in a structural surface (wall, column, vehicle panel) at a known position and angle, providing a directional vector back...