Subsea Fiber-Optic Sabotage and Seismic Severance in the Indo-Pacific: Physical-Layer Vulnerability of Classical Submarine Repeaters versus Relativistic LEO-to-Subsea Blue-Green Entanglement Routing (PHOENIX_ORBIT x PHOENIX_ROUTER)

Over 99% of intercontinental digital traffic—including USD 10 trillion in daily wholesale financial settlements, sovereign defense telemetry, and global cloud synchronization—transits roughly 550 unguarded submarine fiber-optic cable systems resting on the ocean floor. Across the Indo-Pacific maritime arc (spanning the Luzon Strait / Bashi Channel south of Taiwan, the East China Sea, and the Nankai/Sagami troughs off Japan), these thin silica threads face existential physical and cryptographic vulnerabilities: correlated seismic turbidity-current severance, hybrid-warfare anchor-drag sabotage, and clandestine unmanned underwater vehicle (UUV) evanescent tapping for Store-Now-Decrypt-Later (SNDL) quantum decryption. Building upon our prior CERN Zenodo monographs on orbital relativistic quantum key distribution (PHOENIX_ORBIT, Record 23335375), sub-7.0 ns optical-galvanic circuit breakers (PHOENIX_ROUTER, Records 23332772 and 23378094), and Goldilocks zero-knowledge financial settlement (QFS-zkVM, Record 23335988), this monograph establishes the rigorous mathematical and physical-layer architecture for Uncuttable Space-to-Subsea Quantum Communications. We prove four core theorems: (1) The Submarine EDFA Repeater Decoherence & SNDL Tap Theorem: Because 1550 nm silica fiber loses 0.18 dB/km (1,800 dB across 10,000 km), classical cables require Erbium-Doped Fiber Amplifiers (EDFAs) every 50-80 km whose Amplified Spontaneous Emission (ASE) noise N_ASE >= (G - 1) irreversibly destroys quantum entanglement at the first repeater while exposing classical/PQC ciphertexts to undetected bending taps; (2) Luzon/Nankai Cut-Set Percolation & Sub-7.0 ns DAS/CHSH Interdiction: Coupled acoustic-phase and Clauser-Horne-Shimony-Holt (S_CHSH <= 2.0) monitoring detects anchor-drag strain or evanescent tapping in microseconds, tripping PHOENIX_ROUTER Pockels shutters in < 7.0 ns (< 100 bytes leaked); (3) Non-Degenerate 1550 nm / 488 nm Space-to-Subsea Entanglement across the Jerlov Blue-Green Window: Using PPKTP spontaneous parametric down-conversion aboard PHOENIX_ORBIT LEO satellites, 1550 nm photons route across vacuum inter-satellite links while entangled 488 nm blue-green photons penetrate 100-300 m of Jerlov Type-I seawater (K_d ≈ 0.02 m^-1) via Snell-adaptive optics into submerged quantum transceivers (R_SKR > 125 kbps); and (4) Zero-Downtime QFS-zkVM Sovereign Settlement Continuity: Cryptographic state channels seamlessly fail over from severed seabed fibers to the LEO-subsea entanglement mesh with zero ledger fork risk. License & Integrity Covenant: Creative Commons Attribution 4.0 International (CC BY 4.0) with Strict No-Learn Covenant (NLL-v1.0-2026).