NW Sabah — Multi-Model Crustal Observatory · Φ GEOX

Physics chain — mineral physics → rock properties → geophysical signal → testable interpretation

no quantum solver runs here

Material / domain	P–T regime	ρ (kg/m³)	Vp (km/s)	Diagnostic signal	Discriminates
Thinned continental crust (granitoid gneiss)	400–600 °C · 0.5–0.8 GPa	2700–2800	6.0–6.4	Moderate Vp; crust 24–30 km	A · F · R
Underthrust Dangerous Grounds crust	500–800 °C · 1.0–1.8 GPa	2800–2900	6.4–6.8	Dipping low-velocity zone; Moho to ~60 km	A · F
Serpentinised mantle (OCT)	250–500 °C	2600–2750	5.5–6.5	Low Vp + strong magnetisation, no crustal layering	H2-type (not drawn)
Oceanic crust (MORB, 6–7 km)	hydrothermal → 400 °C	2900	6.7–7.2 (layer 3)	Thin high-Vp layer, sharp Moho	E
Ophiolite (serpentinite + spilite)	near-surface	2800–3000	6.0–7.0	Dense + magnetic high; gravity edge	E · F
Kinabalu granite (sheeted laccolith)	~700 °C · 7–12 km depth	2550–2650	5.8–6.2	Local gravity low beneath a dense range	D
Mobile shale (overpressured)	60–90 °C · 2–4 km sub-sea	2200–2400	2.0–2.8	Velocity inversion; weak detachment; mud canopy	B
PSCS slab remnant	250–400 km depth	3300+	8.0+	Teleseismic fast anomaly — not a crustal signal	C

Reality Boundaries & Model Discrimination Engine

evidence object: GEOX-EV-000001 (KMY Broadband)

1. Observed (L0)

Moho depth 32.8 km ± 2.5 km at KMY broadband station (Sidek et al. 2016; Madon 2025). Topography, bathymetry, Tepat-1 well status.

2. Derived (L1)

Airy isostatic root depth 22.9 km calculated from 4,095 m relief. Continuous elastic plate flexure Te = 8–17 km.

3. Interpreted (L2)

Crustal thinning mechanism: Underthrust Dangerous Grounds continental margin (Model A: passes this panel's tests) vs Lithospheric Drip (Model D: fails this panel's tests) — verdicts are scoped to this discrimination panel's observables, not global truth.

4. Assumed

Reference crust thickness T₀ = 30.0 km; crust density 2,800 kg/m³; mantle density 3,300 kg/m³; Young's modulus E = 70 GPa; Poisson's ratio ν = 0.25.

5. Contradicted / Killed

Model D prediction (Moho ≥ 42 km) KILLED by observed 32.8 km (residual = -9.2 km > 2.5 km threshold). Flat 30 km Moho (Model R) also falsified.

6. Missing (Unknown)

Broadband station profile directly under Kinabalu granite summit (0–15 km offset); calibrated 3D velocity model; seismic reflection ties across suture.

All models, same transect

geometry only · status under each

Model-space integrity — geometry hashes

checking…

Every model's crustal architecture (Moho surface + topography + basement) is hashed at runtime. Two models sharing a hash share the same crust — they differ only in what is added on top. That is allowed, but it must be declared, never implied.

#	Model	Crust hash	Full hash	Shares crust with

Falsification tests — numbers, not adjectives

each test can kill its model

Model	Predicted observable	Pass window	Basis	What kills it

Pass windows are the ranges implied by the published constraints summarised in each model's card. They are test specifications, not measurements. No value on this page has been fitted to survey data.
Basis — COMPUTED: derived on this page from the equation shown. PUBLISHED: taken from a cited source. UNKNOWN: no constraint exists, so no window is drawn.

Isostasy check — can a mountain sit on thin crust?

computed live · Airy, ρc 2800 / ρm 3300 kg·m⁻³

e = ((ρ_m − ρ_c) / ρ_m) · (t − t₀)

Crustal thickness t (km, t₀ = 30 km at sea level)

t = 30 km → supports 0.00 km elevation

T₀ sensitivity — the reference is a parameter, so show it

T₀ (km)	t needed	valid for

T₀ is not free: it is fixed by the density pair. ρ_c=2800 with T₀=6 km would place a 6 km granitic column at sea level, which is wrong by ~3.6 km. Oceanic crust (ρ_c≈2900) does need T₀≈39 km for the same reason. The range above is what continental T₀ can legitimately be.

Crust	Supports	Kinabalu 4.095 km?

Flat-plate Airy isostasy, constant densities. It ignores flexural strength and dynamic (mantle) support — which is exactly the point: a summit that Airy cannot support on the local crust is evidence that something other than crustal thickness is holding it up. Flexural support with T_e 8–17 km helps over ~20–35 km wavelengths, not 2.5–5 km deficits.

Control points — 11 stations, WGS84 geodesic chainage

L0 · recomputable

#	Station	Lat	Lon	Chainage (km)

Chainage recomputed between the 11 source coordinates with WGS84 geodesics: 832.84 km overall, 484.90 km to Mt Kinabalu. The coordinates are schematic control points, not surveyed stations — calculation precision does not establish geographic accuracy.

Regional context — GEBCO 2026 basemap

GEBCO 2026 regional bathymetry basemap of NW Borneo and the South China Sea

GEBCO Compilation Group (2026), GEBCO 2026 Grid, DOI 10.5285/4f68d5c7-45eb-f999-e063-7086abc036fa — embedded, attributed, offline. This is a geographic basemap only: it is not a numerically sampled elevation profile and none of the section geometry is traced from it.

Registered but not drawn — three hypothesis families

These are registered hypotheses that carry no geometry on this transect. They are listed so the model space is honest, not so the figure looks complete.

Subduction rollback / back-arc extension — Hall (2013): slab rollback in the Celebes Sea drives extension; predicts regional extension, not a crustal section.
Lithospheric root removal / delamination — predicts a Moho step and magmatic pulse; no along-section geometry published for this line.
Mantle convective support / dynamic topography — Roberts et al. (2018): predicts long-wavelength uplift; a mantle signal, invisible at 70 km depth.

NW Sabah — Multi-Model Crustal Observatory

Models

Section