Toolchest · Datasheet

Seismic Tables — Accumath Toolchest

Dataset: accumath-seismic-tables.csv — 27 rows in one file, split by the table column:

• wave_velocity — 21 rows: P-wave velocity (Vp), S-wave velocity (Vs), and density where the source publishes it, for common materials and for Earth's layers.
• magnitude_energy — 6 rows: moment magnitude 4.0–9.0 in whole-magnitude steps, with energy released in joules and TNT equivalent.

Every value was transcribed from a published table on a page that was opened and read. Nothing was estimated, interpolated, averaged, or computed from a formula. Where no published value could be verified, the cell is blank.

Sources

wave_velocity — materials

• Bourbié, Coussy & Zinszner, Acoustics of Porous Media (Gulf Publishing) — "Typical rock velocities" table (Vp, Vs, density), as reproduced in the Stanford Rock Physics Laboratory teaching slides of Gary Mavko (Stanford University). This one table supplies the water, ice, soil/sediment, sandstone, shale, limestone, dolomite, granite, basalt, coal, and rock salt rows, in m/s and g/cm³ exactly as printed. Where the source's row label is narrower than the dataset's item name, the source label is kept in the item name (e.g. sandstone is the source's "porous and saturated sandstones"; shale is its "saturated shales and clays"; rock salt is its "salt").
• University of Alberta — Geophysics 224 course notes (M. Unsworth), §C1.3 — P-wave velocity table in km/s. Supplies the air row (0.3 km/s) and the gabbro Vp range (6.5–7.0 km/s).
• Guillot et al. (2015), "Tectonic significance of serpentinites," Tectonophysics 646, 1–19 — supplies the gabbro Vs of 3.8 km/s, published there as a single point value (alongside a gabbro Vp of 7.2 km/s; see Conflicts).
• Malusà et al. (2021), "The Deep Structure of the Alps Based on the CIFALPS Seismic Experiment: A Synthesis," Geochemistry, Geophysics, Geosystems 22, doi:10.1029/2020GC009466 — supplies the peridotite row (Vp 7.7–9.0 km/s, Vs 4.4–5.1 km/s, published as the values "typical of peridotite") and both serpentinite rows.

wave_velocity — Earth layers

• PREM — Preliminary Reference Earth Model (Dziewonski & Anderson, 1981), as tabulated in GFZ German Research Centre for Geosciences, Datasheet DS 2.1, "Global 1-D Earth models," compiled by P. Bormann (version October 2011), doi:10.2312/GFZ.NMSOP-2_DS_2.1. PREM tabulates Vp, Vs, and density at discrete depths. Method disclosure: each layer figure in the CSV is the minimum–maximum of the values PREM tabulates across that layer's depth span (crust below the ocean layer to 24.4 km; upper mantle 24.4–670 km; lower mantle 670–2891 km; outer core 2891–5149.5 km; inner core 5149.5–6371 km). These are extractions from a published model table, not ranges printed as ranges by the source, and they are not averages.

magnitude_energy

• VolcanoDiscovery, "How much energy does an earthquake release?" — magnitude/energy comparison table, presented there as following the Gutenberg–Richter magnitude–energy relation. It is the one published table found that gives joules and TNT equivalent together on a single coherent basis, so the CSV rows use it alone, cited per row. (It is not a USGS table, and is not labelled as one.) The source prints energies as e.g. "6.3 x 10¹⁰"; the CSV writes the same values in e-notation (6.3e10).

Wave types

Wave	Type	Particle motion	Travels through	Relative speed
P (primary)	Body wave — compressional / longitudinal	Parallel to the direction of propagation (push–pull)	Solids, liquids, and gases	Fastest; arrives first
S (secondary)	Body wave — shear / transverse	Perpendicular to the direction of propagation	Solids only	Slower than P; arrives second
Rayleigh	Surface wave	Retrograde elliptical motion in the vertical plane containing the propagation direction	Along a free surface or boundary	Slower than S in a uniform medium; dispersive in a layered Earth
Love	Surface wave	Horizontal, transverse to the direction of propagation (like an S wave confined to a surface layer)	Requires a layered structure	Dispersive; travels in the surface layer

Facts as stated in the University of Alberta Geophysics 224 notes (§C1): in a liquid the shear modulus is zero, so S waves cannot propagate in a liquid, while P waves can. That single fact drives the shadow-zone reasoning below and is why the vs column is blank for air and water in the CSV: fluids carry no shear waves. (In PREM the outer core's Vs is tabulated as exactly 0, and that published 0 is what the CSV records for the outer core.)

The S-wave shadow zone

Because the outer core is liquid, no S wave can cross it. Direct S waves from an earthquake are therefore not observed at stations whose ray paths would have to pass through the core — the S-wave shadow zone. P waves do enter the core, but they are strongly refracted at the core–mantle boundary (P velocity drops from ~13.7 km/s in the deepest mantle to ~8.1 km/s in the outer core, per the PREM rows in this dataset), which bends them away from an annular band of stations and produces the P-wave shadow zone as well. The absence of direct S waves beyond the shadow zone, together with the P-wave refraction pattern, is the standard published evidence that Earth's outer core is liquid — and the return of a finite Vs (3.50–3.67 km/s in PREM) in the inner core is part of the evidence that the inner core is solid.

Magnitude and energy

The Gutenberg–Richter energy relation (a published formula, stated here as a formula only — it was not evaluated to produce any CSV value):

log₁₀ E ≈ 1.5 M + 4.8, with E in joules.

USGS publishes a different relation on its "Earthquake Magnitude, Energy Release, and Shaking Intensity" page:

log E = 5.24 + 1.44 Mw

The two relations have different constants and are kept distinct here; neither was used to fill the CSV.

Step factors (published): each whole-number magnitude increase is a ×10 increase in measured amplitude and about a ×32 increase in energy released (USGS). USGS's The Severity of an Earthquake (General Interest Publication) tabulates the intermediate steps as well: a 0.5 magnitude increase is ×3.2 in ground motion and about ×5.5 in energy; 0.3 is ×2.0 and about ×3; 0.1 is ×1.3 and about ×1.4.

Why the CSV has whole magnitudes only — and a documented conflict

The requested 0.5-step span (4.0–9.5) could not be filled from a qualifying published table: no authoritative published table of joules and TNT equivalent at half-magnitude steps was found, and computing the half steps from the formula was prohibited by the dataset rules. The CSV therefore carries the whole-magnitude steps the chosen table actually publishes (4.0–9.0). The 9.5 step is likewise absent — the chosen table stops at 9.0.

Published TNT equivalences also conflict with each other by large factors, which is why only one table's basis is used in the CSV:

Source	M4.0 equivalent
VolcanoDiscovery table (used in the CSV)	15 tons of TNT (with 6.3 × 10¹⁰ J)
USGS, "Earthquake and energy comparisons" chart (updated 2025)	56,000 kg of explosive equivalent (chart gives kg, whole magnitudes M2–M10, and does not state joules)
USGS Hawaiian Volcano Observatory, "Volcano Watch" article	≈ 1,000 tons of TNT (it gives M1.0 ≈ 70 lb TNT, M2.0 ≈ 1 metric ton)

These figures rest on different energy conventions and are not interchangeable. They are recorded here so the conflict is visible; the CSV does not mix them.

Magnitude vs intensity

Magnitude and intensity are different quantities. Magnitude is a single number for the earthquake itself — the size of the source, tied to the energy released (this dataset's second table). Intensity describes the shaking and its effects at a particular place: one earthquake has one magnitude but many intensities, varying with distance from the epicentre, rupture direction, focal depth, and local ground conditions. The United States uses the Modified Mercalli Intensity scale for intensity — see the companion dataset accumath-mercalli-scale.csv. A magnitude table must never be read as an intensity prediction for a given town.

Caveats

• Velocities are not constants of nature. Seismic velocities in a given material vary with pressure (depth), temperature, porosity, fracturing, pore-fluid type and saturation, bulk composition, and — in foliated or crystalline rocks — the direction of propagation relative to the fabric (anisotropy). The CSV carries published typical ranges (and, for the Earth layers, a published reference model's values), not specifications. The spread within each printed range is real information and was deliberately not collapsed.
• Serpentinite is the extreme case: its velocity depends on which serpentine mineral dominates and on the degree of serpentinization, so the dataset carries two rows (lizardite and antigorite) rather than one false "serpentinite" number. A partly serpentinized peridotite falls between the peridotite and serpentinite rows.
• Conflicts recorded, not resolved:
• Inner core Vs: one widely used textbook table (Earle, Physical Geology, 2nd ed.) prints inner-core Vs as 0. That conflicts with PREM (3.50–3.67 km/s) and with the modern understanding that the inner core is solid. The CSV follows PREM; the textbook's 0 was not copied.
• Peridotite Vp: University of Alberta notes give "ultramafics" as 7.5–8.5 km/s; Malusà et al. (2021) give peridotite as 7.7–9.0 km/s. The CSV uses the Malusà et al. range because that source publishes Vp and Vs as a pair; the Alberta range stands here in the notes.
• Gabbro: Guillot et al. (2015) quote gabbro Vp 7.2 km/s as a point value, just above the Alberta table's 6.5–7.0 km/s range. The CSV's Vp is the Alberta range and its Vs is Guillot et al.'s 3.8 km/s point value; each cell's source is named on the row.
• Blank cells are deliberate. Gabbro, peridotite, and the serpentinites have no density in the CSV because no generic published density range for them was verified on an opened reference table — laboratory specimen values exist in the literature but are measurements of particular samples at stated pressure/temperature, not generic table values, and were not dressed up as such. Air has no density because the Alberta table does not publish one.
• Units are per row. The materials table was published in m/s; the Alberta, review-paper, and PREM values in km/s. Units are recorded in the vp_unit / vs_unit columns rather than silently converted, so every number reads exactly as its source printed it (km/s values are, of course, m/s ÷ 1000, but no converted figure appears in the CSV).
• Energy figures are radiated seismic energy estimates on the stated relation's basis, not total strain energy release, and TNT equivalence is a comparison device, not a claim that an earthquake behaves like an explosion at a point.

Legal basis

Facts are not copyrightable (Feist v. Rural Telephone), and the values here are raw published facts restated in our own dataset with the source named on every row — no source's database file, table image, or expressive text was reproduced. USGS and GFZ material is government-published (US federal works are public domain under 17 U.S.C. § 105); the remaining values come from openly published university teaching material and scholarly journal articles, used as facts with attribution.