Seismology Tools
Browse all available seismology tools.
Available tools
- ADC Clip Level Full Scale Counts Calculator Digitizer LSB size and clip voltage from bit depth and full-scale range.
- ADC Effective Bits Noise Floor Calculator Effective number of bits from the measured SNDR: ENOB = (SNDR − 1.76)/6.02.
- Aftershock Zone Length Utsu Scaling Calculator Utsu aftershock-zone scaling: log₁₀L(km) = 0.5·M − 1.8, with equivalent area.
- AGC Gain Step Artifact Flagger Flag windows where automatic-gain-control steps coincide with event energy.
- Air Coupled Rayleigh Wave Speed Calculator Rayleigh wave speed from shear velocity (≈0.92·β for ν = 0.25) compared with the speed of sound in air.
- Amplification Borcherdt Factor Lookup Borcherdt-style short-period amplification factor from NEHRP class.
- Annual Rate To T Years Exceedance Converter Convert an annual exceedance rate to the probability of exceeding at least once in T years.
- Antialias Filter Corner Nyquist Checker Check that a low-pass corner sits safely below the Nyquist frequency of the sample rate.
- Apparent Dip Along Section Line Calculator Apparent dip on a section making angle α with the strike: tan(δ_app) = tan(δ)·|sin α|.
- Apparent Stress Energy Ratio Calculator Apparent stress σ_app = μ · Es / M₀ in megapascals.
- Arias Intensity Duration Proxy Calculator Arias intensity proxy I_a ≈ (π/2g)·∫a² dt approximated by PGA² times effective duration.
- Array Aperture Moveout Resolution Checker Check whether array aperture resolves the expected moveout across the slowness band.
- Asperity Area Fraction Scaling Calculator Asperity area fraction A_a/A₀ as a power-law function of seismic moment, capped at the physical upper bound of one.
- Attenuation Quality Factor Q Calculator Infer quality factor Q from amplitude decay along a propagation path: A = A₀·exp(−π f x / (Q v)).
- Average Moment Rate From Moment Duration Calculator Average seismic moment release rate over a specified source duration: Ṁ₀ = M₀/T.
- Average Radiation Factor Boore Boatwright Lookup Boore-Boatwright style average radiation factors for P and S waves over the focal sphere.
- Azimuthal Hole Location Bias Warning Checker Warn when the station azimuthal gap is wide enough to push hypocentres systematically into the gap.
- B Value Standard Error Shi Bolt Formula Shi & Bolt (1982) b-value uncertainty, simplified for unit-variance magnitude residuals: σ_b = 2.30·b²/√(N−1); supply magnitude residuals for the full Σ(Mᵢ−M̄)² form.
- Basin Edge Surface Waves Checker Screen whether the bedrock-to-basin shear-wave velocity contrast reaches an illustrative 2:1 threshold associated with stronger basin-edge effects; geometry is not modeled.
- Bath Law Largest Aftershock Gap Note Lookup Båth's law: the largest aftershock sits about 1.2 magnitude units below its mainshock.
- Between Event Tau Variance Calculator Between-event tau variance decomposition across multiple events.
- Blind Zone Hidden Layer Depth Checker Flag layers that cannot produce a critically refracted first arrival because their velocity does not exceed every overlying layer velocity.
- Borehole PS Logging Average Velocity Calculator Interval and average shear velocities from downhole first-arrival times at two depths.
- Brune Corner Frequency Source Model Calculator Compute the Brune (1970) circular-crack corner frequency fc = 4.9e6·β·(Δσ/M₀)^(1/3) with β in km/s, Δσ in bar, and M₀ in dyn·cm.
- Brune Displacement Spectrum Peak Frequency Note For the Brune model, displacement amplitude peaks exactly at the corner frequency.
- Brune Source Time Duration From Corner Calculator Characteristic source duration from the Brune corner frequency: τ_c ≈ 1/(2π f_c).
- Catalog Complete Timespan Denominator Checker Verify the catalog window is long enough for stable annual-rate denominators.
- Catalog Depth Histogram Binner Bin hypocentral depths into fixed-width bins with an out-of-range tail count.
- Catalog Magnitude Type Histogram Summary Count catalog magnitudes by reported type (ml, mb, ms, mw, other).
- Characteristic Earthquake Magnitude Window Lookup Estimate characteristic magnitude from a fault length using the Wells & Coppersmith strike-slip relation.
- Clock Drift PPM Linear Regression Calculator Least-squares drift rate in parts-per-million from timing offsets versus elapsed days.
- Coda Duration Magnitude Nuttli Formula Calculator Nuttli-style coda-duration magnitude M_d = a + b·log₁₀(τ) + c·Δ with regional coefficients.
- Coda Normalization Lapse Time Amplitude Correction Correct coda amplitudes to a reference lapse time using the spreading law A ∝ t^−α.
- Coda Q Scattering Intrinsic Split Calculator Split total attenuation into intrinsic and scattering parts via 1/Q_total = 1/Q_intrinsic + 1/Q_scattering.
- Completeness Magnitude Max Curvature Calculator Mc from the maximum-curvature (mode) of the binned frequency-magnitude distribution.
- Corner Frequency Stress Drop Consistency Checker Invert the Brune relation fc = 0.49·β·(Δσ/M₀)^(1/3) for stress drop Δσ = M₀·(fc/(0.49·β))³ given the moment and compare with a claimed Δσ; no rigidity term is needed because Δσ/M₀ replaces it.
- Coulomb Stress Change On Receiver Plane Calculator Coulomb failure stress change on a receiver plane: ΔCFF = Δτ + μ′·Δσn (tension positive convention).
- Critical Reflection Angle Post Critical Note Checker Critical angle for a reflecting interface from velocity contrast, with post-critical guidance.
- Cumulative Absolute Velocity CAV Calculator CAV = Σ|a|·Δt over uniformly sampled acceleration.
- Cumulative Moment Release Catalog Summary Total moment and equivalent single-event magnitude of an event list.
- Damping Response Spectrum Heuristic Scaling Heuristic spectral scaling from 5% to another damping ratio: F = (0.05/ζ)^0.25.
- DART Pressure Tsunami Flag Checker Flag DART bottom-pressure observations whose amplitude and period band match a tsunami signature.
- Dataless Channel Epoch Overlap Checker Detect whether two channel epochs overlap and quantify the overlap span.
- Deaggregation Mean Mag Dist Epsilon Calculator Weighted mean magnitude, distance, and epsilon from deaggregation bins.
- Decimation Factor Aliasing Note Lookup Validate an integer decimation factor and report the output rate and anti-aliasing guidance.
- Declustering Retained Event Fraction Summary Fraction of the catalog retained as Poissonian background after declustering.
- Depth Conversion Average Velocity Method Calculator Convert an event's one-way time to depth with a constant average velocity.
- Depth Phase PP Minus P Depth Estimate Crustal depth from the pP−P time assuming a surface bounce: h ≈ Δt·v̄/2.
- Deterministic vs Probabilistic Split Guide Recommend DSHA or PSHA based on available fault characterization and recurrence data.
- Digitizer Input Loading Error Percent Calculator Voltage divider loading error when a sensor drives the digitizer input impedance.
- Dip-Slip Seismic Moment and Average Dislocation Estimate Seismic moment and average dislocation estimate for a dip-slip rupture: geodetic moment M₀ = μ·A·ū plus a heuristic vertical offset scale; this tool does NOT solve the Okada (1992) elastic half-space displacement field.
- Dipping Refractor True Velocity UpDown Dip Calculator True refractor velocity from updip/downdip apparent velocities: V₂ = 2V_uV_d·cosα/(V_u+V_d).
- Directivity Narrowband Pulse Period Calculator First-order rupture-duration proxy for directivity pulse period: T_p ≈ L/v_r.
- Directivity Pulse Duration Near Source Calculator Forward-directivity timescale for a unilateral rupture, L·(1/v_r − 1/β), assuming the site lies along strike in the rupture direction.
- Double Couple P T Axis Plunge Style Shortcut Shortcut P/T axis plunges for ideal focal styles (strike-slip, normal, reverse).
- Double Difference Pair Mean Offset Summary Summarize double-difference relocation pairs: mean and RMS inter-event separation.
- Elapsed Time Last Event Segment Checker Compare elapsed time since the last segment rupture against the mean recurrence interval.
- Elevation Static Correction Replacement Velocity Calculator Elevation static from station height above datum using the replacement-velocity method.
- EMS98 Vulnerability Intensity Band Crosswalk EMS-98 damage-grade onset bands by building vulnerability class.
- ETAS Aftershock Productivity Alpha Calculator Relative ETAS-style aftershock productivity 10^[α(M−Mc)]. It omits the fitted productivity constant and Omori time integral, so it is a relative factor rather than an expected event count.
- Eurocode 8 Ground Type Lookup EN 1998-1 Table 3.1 ground type from VS30: >800 m/s A, 360–800 B, 180–360 C, and <180 D. Type E is not inferred because its definition requires stratigraphic information beyond VS30.
- Event Count Poisson Confidence Interval Gehrels Approximation Gehrels (1986) algebraic approximations to the 84.13% one-sided Poisson limits (the conventional asymmetric one-sigma error bars), including the tabulated 1.841 upper limit for zero counts.
- Fault Seismic Moment Deficit Calculator Compare seismic moment captured over a window against the tectonic budget μ·A·V·T.
- Felt Radius Heuristic Log Scaling Calculator User-parameterized log-linear felt-radius screen R = R₀·10^(kM). The default R₀=0.1 km and k=0.5 are illustrative and must be calibrated for regional attenuation, depth, and reporting conditions.
- First Break SNR Validity Flagger Screen first-break picks against a minimum signal-to-noise ratio in decibels.
- First Motion Polarity Beachball Quadrant Picker Summarize P-wave first-motion polarity statistics into beachball quadrant occupancy.
- Focal Style Rake Band Classifier Classify focal-mechanism style from the rake angle using standard Aki-Richards bands.
- Foreshock Mainshock Probable Classifier Classify a smaller event as probable foreshock based on its proximity in time and distance to a larger successor.
- Fracturing Monitor Magnitude Reporting Lookup Illustrative local-magnitude bands for hydraulic-fracturing monitoring. Traffic-light thresholds are jurisdiction- and project-specific, so operational decisions must use the approved site protocol.
- Galvanometer Damping 0707 Lookup Classify instrument damping against the maximally-flat ζ = 0.707 benchmark.
- Gardner Knopoff Declustering Window Lookup Gardner-Knopoff space window by mainshock magnitude for catalog declustering.
- Geometrical Spreading Body Wave Calculator Body-wave geometrical spreading amplitude decays as 1/r relative to a reference distance.
- Geophone Natural Period Response Corner Lookup Response corner and usable band for common geophone classes by natural frequency.
- Geophone Spring Max Acceleration Range Checker Mass-spring clip level: a_max = ω₀²·x_max expressed in g.
- GMM Total Dispersion Tau Sigma Combine Calculator Total GMM dispersion σ_T = √(τ² + σ²).
- GMPE Log Distance Attenuation Calculator Simplified GMPE ground-motion attenuation with log-distance spreading.
- GPS Clock Jitter MS Budget Calculator Timing jitter converted to equivalent travel-time distance bias at P-wave speed.
- GPS Week Second To Days Since Era Converter Convert GPS week/seconds-of-week to days since the GPS era start (1980-01-06) with rollover count.
- Group vs Phase Velocity Difference Calculator Group velocity U = c − λ·dc/dλ from phase velocity and its wavelength gradient.
- Gutenberg Richter A Value Annual Normalization Annualized GR productivity: a = log₁₀(N_year) + b·Mc.
- Gutenberg Richter B Value Two Anchor Fit b-value from two cumulative-count anchors of the Gutenberg-Richter law.
- Hazard Curve Probability Interpolation Log-Log Log-log interpolation of annual exceedance probability between hazard-curve anchors.
- Head Wave Critical Angle Appearance Calculator Critical angle i_c = arcsin(V₁/V₂); no head wave exists when V₁ ≥ V₂.
- Housner Spectral Intensity Calculator SI(Housner) = integral of PSV over 0.1–2.5 s approximated by trapezoid over supplied spectral velocities.
- HVSR Clear Peak Confidence Checker SESAME-style screening: amplitude prominence plus window-to-window frequency stability.
- HVSR Nakamura Peak Frequency Calculator Fundamental site frequency from the peak of an H/V spectral-ratio curve.
- Icequake Glacial Magnitude Range Lookup Characteristic magnitude ranges for glacial earthquake mechanisms.
- Injection Pressure Trigger Threshold Checker Screen injection wellhead pressure against a pore-pressure perturbation threshold.
- Instrument Response Gain DB Lookup Convert a dimensionless gain factor to decibels (20·log₁₀).
- Intensity PGA Wald 1999 Table Lookup Wald et al. (1999) MMI-to-PGA bounds used in ShakeMap ground-motion to intensity conversion.
- Iribarren Surf Similarity Runup Regime Classifier Deep-water Iribarren number ξ = tanβ/√(H/L₀) and the conventional spilling, plunging, or surging breaker classification.
- Isoseismal Annulus Area Between Intensities Calculator Felt area of the annulus between two intensity contours using the Kövesligethy decay.
- JMA Intensity From PGV Converter Japan Meteorological Agency instrumental intensity from PGV (cm/s): I_JMA = 2.68·log₁₀(PGV) + 2.29 (approx).
- Joint Hypocentral Grid Search Step Calculator Grid search step sized to half the target location tolerance (Nyquist-style sampling of the misfit surface).
- Kappa Site Anelastic Attenuation Calculator Site anelastic attenuation factor exp(−π κ f) at a given frequency.
- Kovesligethy Intensity Decay Isoseismal Calculator Kövesligethy isoseismal radius: I(r) = I₀ − 3·log₁₀(√(r²+h²)/h), inverted for a target intensity.
- Liquefaction Feature Magnitude Bound Lookup Ambraseys-style minimum magnitude bound for liquefaction at a given epicentral distance.
- Location Formal Error Scale Factor Calculator Heuristic horizontal formal error: σ_h ≈ RMS·v_p·√(N/(N−4)).
- Love vs Rayleigh Motion Classifier Screen surface-wave component amplitudes for Love-like SH dominance or Rayleigh-like P-SV dominance. Amplitudes alone cannot determine ellipticity or retrograde phase motion.
- Love Wave Dispersion Period Speed Lookup Illustrative fundamental-mode Love-wave phase-speed bands for a generic continental crust. Real dispersion must be calculated from a site-specific velocity model.
- Macroseismic Weighted Centroid Calculator Intensity-weighted centroid of macroseismic observations as a first epicenter proxy.
- Magnitude Frequency Entropy Shannon Calculator Shannon entropy H = −Σ p·log₂p over magnitude-bin probabilities.
- Magnitude Scaling Saturation Check Tool Flag whether a rupture length implies magnitude beyond the empirical saturation limit (~M7.8) of simple linear scaling.
- MB To MW Bandwise Conversion Lookup Bandwise mb-to-Mw conversion with a saturation note above mb ≈ 6.5.
- Mercalli vs JMA Crosswalk Lookup Crosswalk between JMA instrumental scale and equivalent MMI range.
- Microtremor Array Resolution Frequency Band Checker Check that array aperture brackets the wavenumbers of the target frequency band for SPAC/f-k dispersion work.
- Mining Collapse Magnitude Norms Lookup Illustrative magnitude bands for mining-induced events. It does not identify the source mechanism or replace mine-specific safety, evacuation, and inspection thresholds.
- MiniSEED Channel Identifier Validator Validate miniSEED/FDSN channel identifier rules — NSLC code lengths, printable characters, and the '--' placeholder for an empty location — and assemble NET.STA.LOC.CHA; this is not a binary SEED record parser.
- Moment From Spectral Flat Level Calculator Compute seismic moment from the low-frequency spectral plateau Ω₀ using the Brune spectral model.
- Moment Magnitude From Moment Hanks Kanamori Convert seismic moment to moment magnitude: M_w = (2/3)(log₁₀M₀ − 9.1).
- Moment Tensor Double Couple Percent Decomposition Calculator Decompose ordered moment-tensor eigenvalues into isotropic and deviatoric amplitudes, then split the deviatoric share into double-couple and CLVD components; the three reported percentages sum to 100.
- MS MB Explosion Discrimination Note Lookup First-order Ms/mb discrimination screen for event source type.
- Near Fault Fling Step Velocity Pulse Calculator Fling-step peak velocity from static slip and rise time: v ≈ Δu / τ.
- Nearest Neighbor Space Time Linkage Distance Normalized nearest-neighbor distance for each event against all others.
- NEHRP Fundamental Period Site Lookup Site fundamental period Ts = 4H/Vs from a NEHRP class-typical profile depth and velocity.
- Network Cluster Singleton Fraction Quality Cluster-analysis quality screen: fraction of unassociated singletons in a detected cluster set.
- Network Detection Threshold Coverage Calculator Illustrative magnitude-of-completeness screening relation M_min ≈ 1.5 + log₁₀(r/km) using a detection radius of 1.5 times station spacing; it is not a calibrated network threshold.
- Network Station Uptime Percent Calculator Station uptime percentage from total and outage days.
- Nonlinear Soil Strain Degradation Lookup Shear modulus reduction (degradation) factor for soil at a given cyclic shear strain.
- Normal Incidence Two Way Time Thickness Calculator Layer thickness from normal-incidence two-way time and interval velocity.
- Offset Feature Cumulative Slip Per Event Calculator Average per-event slip from cumulative offset divided by the number of events recorded.
- Omori Law Aftershock Decay Rate Calculator Modified Omori law daily aftershock rate n(t) = k/(t+c)^p.
- P Wave Azimuthal Residual Vector Sum Split Summarize the first azimuthal harmonic of P-wave residuals and use a least-squares cosine/sine fit to separate systematic directional variation from residual scatter.
- P Wave Modulus Constrained Calculator Compute the P-wave modulus M = ρ·Vp².
- Paleoseismic Trench Event Horizon Count Tool Count earthquake event horizons between dated units from trench stratigraphy flags.
- Peterson Noise Model Low High Lookup Approximate NLNM/NHNM acceleration power (dB relative to 1 (m/s²)²/Hz) at a period, log-linearly interpolated from a reduced set of Peterson (1993) anchors.
- PGV PGA Correlation Approximation Calculator Approximate PGV from PGA by treating the motion as a sinusoid with effective period T_ref: PGV ≈ PGA·T_ref/(2π); this is a kinematic estimate, not an empirical ground-motion conversion.
- Plus Minus Delay Time Refraction Method Tool Intercept/delay-time method: recover interface depth from the reversed-profile intercept time t_i = 2h·cos(i_c)/V₁.
- Poisson Return Period Probability Exceedance Calculator Probability of at least one exceedance within T years for a Poisson process: P = 1 − exp(−T/TR).
- Principal Tide Constituent Period Lookup Periods of the principal tidal constituents relevant to tidal-triggering studies.
- Quarter Wave Layer Higher Mode Harmonics Calculator Quarter-wavelength harmonics f_n = (2n−1)·Vs/(4H) for a layer over stiff half-space.
- Radiated Energy From Magnitude Gutenberg Richter Gutenberg-Richter energy relation log₁₀Es(J) = 1.5·M + 4.8.
- Radiated Energy Moment Ratio Calculator Dimensionless ratio of radiated seismic energy to seismic moment.
- Ray Parameter Slowness Apparent Velocity Converter Convert horizontal slowness (s/deg) to apparent velocity using 111.195 km/deg.
- Reasenberg Space Time Window Lookup Reasenberg-cluster linkage parameters (interaction radius and look-ahead time) by magnitude class.
- Recurrence Interval Slip Rate Event Slip Calculator Characteristic recurrence from per-event slip and long-term slip rate: T = D/V.
- Reduced Travel Time Plot Converter Convert absolute travel times to reduced times t − Δ/v_red for slowness plotting.
- Refraction Layer Crossover Distance Calculator Crossover distance where direct and head waves arrive together: x_c = 2h·√((V₂+V₁)/(V₂−V₁)).
- Renewal BPT Coefficient Variation Calculator Brownian Passage Time coefficient of variation α = σ/μ and its relation to aperiodicity.
- Repeating Pair Slip Compatibility Checker Check whether two repeating events' implied slips are compatible given their areas and moments.
- Reservoir Induced Stress Change Bar Calculator First-order Coulomb stress perturbation under a reservoir load: Δσ ≈ ρ·g·h.
- Resonance Quarter Wavelength Soft Soil Calculator Soft-soil resonant frequency f₀ = Vs/(4H) for a layer over rigid bedrock.
- Response Poles Zeros Consistency Checker Validate an analog response stage: pole/zero counts and normalization sanity.
- Response Spectrum Corner Period Band Lookup Acceleration- and velocity-controlled period bands scaled by magnitude class.
- RMS Travel Time Residual Quality Calculator Root-mean-square travel-time residual and qualitative location quality.
- RMS Velocity Dix Equation Interval Velocity Calculator Dix equation interval velocity between two horizons from RMS velocities and zero-offset times.
- Rupture Velocity Shear Wave Ratio Checker Classify rupture velocity as sub-shear or super-shear relative to β.
- S-P Interval Hypocentral Distance Calculator Hypocentral distance from the S-minus-P interval in a single-layer model: d = Δt / (1/V_s − 1/V_p).
- S-Wave Nodal And Maximum Azimuth Lookup Nodal and maximum-radiation azimuths of the strike-slip S-wave pattern R ∝ sin 2(az − φ).
- Scalar Moment From Deviatoric Eigenvalues Calculator Scalar seismic moment from tensor eigenvalues: M̄ = √(Σλᵢ²/2).
- Schuster Critical Value Significance Checker Assess tidal-phase Schuster test significance from the standardized statistic z.
- Seismic Efficiency Energy Partition Calculator Seismic efficiency η = Es / E_total with E_total = (Δσ/2μ)·M₀.
- Seismic Landslide Area Volume Scaling Calculator Empirical area-volume scaling for seismically triggered landslides: V = α·A^γ (Guzzetti-like).
- Seismic Moment To Slip Displacement Back Calc Average slip from moment and area: D = M₀/(μ·A).
- Shake Alert Lead Time Seconds Estimate Calculator EEW lead time at a target site: S arrival minus detection epoch (P travel plus processing latency).
- ShakeMap Instrument Intensity PGV Converter Convert PGV to instrumental intensity with the Wald et al. (1999) ShakeMap relation MMI = 3.51·log₁₀(PGV in cm/s) + 2.35, clamped to the displayed MMI range 1–10.
- Significant Duration Arias 5 To 95 Calculator Significant duration bracketing the 5–95% Arias interval from per-interval energy contributions.
- Site Class NEHRP From VS30 Lookup NEHRP site class (A–E) from time-averaged shear velocity.
- Site Kappa Path TStar Decomposition Split measured kappa into site term and path t*: κ_meas ≈ t* + κ₀.
- Site Kappa Zero By NEHRP Class Lookup Typical near-surface kappa ranges by NEHRP site class.
- Slip vs Time Predictable Checker Check whether observed recurrence interval and slip are consistent with a loading-rate-driven recurrence model.
- Slow Slip Equivalent Magnitude Duration Scaling Calculator Equivalent moment magnitude of a slow-slip episode from plate-rate slip accumulated over its duration.
- Source Rise Time Dislocation Calculator Characteristic source timescale estimated as fault width divided by shear-wave velocity; this is a dimensional proxy, not a fitted rupture rise-time model.
- Source Spectral Falloff High Frequency Slope Checker Check whether a fitted high-frequency spectral decay matches the Brune γ=2 expectation.
- Spatial Grid Cell Count Density Summary Bin event eastings/northings into a square grid and report cell occupancy statistics.
- Spectral Ratio Two Station Q Estimate Calculator Two-station coda Q from the log spectral-ratio slope: ln(A₁/A₂) = −π f Δt / Q.
- Station Gap Azimuthal Coverage Degree Calculator Largest azimuthal gap between consecutive stations around an epicenter.
- Station Residual Outlier Sigma Flagger Flag stations whose travel-time residuals exceed k standard deviations of the set.
- Stoneley Interface Necessary-Condition Checker Check the necessary solid-solid shear-support condition for a Stoneley interface wave. Positive shear speeds on both sides are necessary but not sufficient; density and compressional-wave speed are also needed for a full existence test.
- Strain Drop Slip Over Length Stress Drop First-order stress drop from the strain-drop picture: Δσ ≈ μ·(D/L).
- Strike Dip Plane Normal Vector Converter Unit normal of a plane from strike/dip in ENU axes: n = (cosφ·sinδ, −sinφ·sinδ, cosδ).
- Strike-Slip Seismic Moment and Average Dislocation Estimate Seismic moment and average dislocation estimate for a strike-slip rupture: geodetic moment M₀ = μ·A·ū and a half-slip (ū/2) offset scale; this heuristic does NOT compute the Okada (1992) elastic half-space spatial displacement field.
- Strong Motion Linear Baseline Correction Remove linear baseline drift fitted on the record tail and report the corrected peak.
- Surface Rupture Length Scaling Lookup Classify expected surface-rupture behavior by magnitude band.
- Surface Wave Magnitude VK20 Formula Calculator Classic vertical-component Rayleigh surface-wave magnitude Ms = log10(A/T) + 1.66·log10(Δ°) + 3.3 with A in micrometres; nanometre input is converted to µm internally.
- Surface Wave Spreading Half Space Calculator Surface waves in a half-space spread geometrically as 1/√r.
- Survey Design Fold Count CMP Binning Summary Nominal 2-D end-on acquisition fold N·Δr/(2·Δs) and CMP interval Δr/2 for a regular source/receiver grid; actual edge fold and irregular geometry require explicit trace counting.
- Swarm Vs Mainshock Aftershock Sequence Classifier Classify a sequence as swarm or mainshock-aftershock from the largest-event dominance and duration.
- Synthetic Strike-Slip Polarity Data Generator Generate synthetic P-wave polarity training data for a strike-slip-dominant focal mechanism.
- Tau-P Travel Time Anchor Interpolation Calculator Linearly interpolate P travel time between supplied distance anchors.
- Telemetry Block Gap Detector Locate telemetry blocks whose sample counts fall below the expected quota.
- Tidal Harmonic Residual RMS Calculator RMS and peak residual between observed tide-gauge series and a harmonic prediction.
- Tidal Stress Phase Trigger Checker Check whether an event's tidal phase falls in the promoting window for its fault style.
- Tide Gauge Bottom Pressure Hydrostatic Depth Converter Convert bottom-pressure to equivalent sea-surface height via the hydrostatic relation h = p/(ρg).
- Time Dependent Conditional Probability Calculator Approximate time-dependent rupture probability from a Weibull renewal model, using k = (mean/std. dev.)² and a scale chosen to preserve the supplied mean; this is not a Brownian-passage-time calculation.
- Tomography Ray Density Cell Coverage Calculator Cell hit density: total ray-path length inside the cell divided by cell size.
- Topographic Aggravation Factor Ridge Calculator Illustrative ridge-top ground-motion amplification screen based on slope and height-to-wavelength ratio; it is not a code-prescribed Eurocode 8 factor.
- Tremor Slip Episodic Weeks Lookup Typical episodic-tremor-and-slip recurrence and migration parameters by region class.
- Tri Station Circle Epicenter Least Squares Solver Epicenter from three S-P distance circles via Gauss-Newton least squares.
- Tsunami Open Ocean Travel Time Shallow Water Calculator Long-wave travel time t = R/√(g·h) across a uniform-depth ocean.
- Tsunami Runup Empirical Okal Synolakis Lookup First-order far-field tsunami runup scaling with magnitude and distance (heuristic exponents).
- Tsunami Seafloor Vertical Offset Calculator First-order seafloor vertical offset from dip-slip on a fault: u ≈ slip·sin(dip).
- Tsunamigenic Magnitude Threshold Checker Screen whether an event magnitude exceeds common tsunamigenic thresholds for its setting.
- Uniform Hazard Spectrum Interpolation Calculator Log-log interpolated UHS ordinate at an arbitrary period from anchor ordinates.
- Velocity Model Layer Cake Two Way Time Depth Converter Depth from two-way time through a layer-cake velocity model.
- Vertical Horizontal VH Ratio Lookup Typical vertical-to-horizontal spectral ratio by period band.
- Volcano Repeater Family Correlation Checker Screen whether an event group qualifies as a repeating-earthquake family via waveform similarity and regularity.
- VP VS Ratio Poisson Checker Compute Vp/Vs and the implied Poisson ratio, flagging unphysical values.
- VS30 Time Averaged Shear Velocity Calculator Time-averaged shear velocity over the top 30 m: VS30 = 30 / Σ(dᵢ/Vsᵢ).
- Wadati Diagram VP VS Slope Calculator Recover Vp/Vs from the Wadati diagram slope k (t_s−t_p = k·t_p): Vp/Vs = k + 1.
- Wadati Origin Time Single Station Formula Calculator Origin-time estimate from one station using the Wadati ratio: t₀ = (R·t_p − t_s)/(R − 1).
- Wadati Residual Histogram Binner Bin station Wadati residuals into a fixed-width histogram with outlier tail capture.
- Well Log Acoustic Impedance Reflection Coefficient Normal-incidence reflection coefficient from acoustic impedances: R=(Z₂−Z₁)/(Z₂+Z₁).
- Within Event Sigma Lambda Calculator Convert within-event sigma to a standard deviation in natural-log units and its fractional spread.