Category
Geology & Earth Science
Geology and earth science formulas and calculators for seismology and hydrogeology used to understand Earth's structure and behavior. Includes wave propagation, groundwater flow, and rock mechanics equations.
29Formulas
2Subcategories
Updated Oct 2026
Seismology
Tsunami Calculator – Speed, Arrival Time & Impact Tool
Multiple
Hydrogeology
Flood Recurrence Interval (Weibull Formula)
T = (n+1) / m
Hydrogeology
Drainage Basin Relief Ratio
Rh = Relief / Basin Length
Hydrogeology
Gravimetric Soil Moisture Content
w (%) = ((Mass_wet - Mass_dry) / Mass_dry) * 100
Seismology
Rock/Mineral Density (Specific Gravity)
SG = Density of Sample / Density of Water
Seismology
Geothermal Gradient
Gradient = ΔT / Δd
Hydrogeology
Stream Gradient
Gradient = Elevation Drop / Stream Length
Hydrogeology
Stream Discharge
Q = V * A
Hydrogeology
Groundwater Seepage (Linear) Velocity
v_s = v / n
Hydrogeology
Well Specific Capacity
Sc = Q / s
Hydrogeology
Groundwater Recharge Rate
R = P - ET - RO
Hydrogeology
Porosity
n = (Vv / Vt) * 100
Hydrogeology
Specific Yield (Unconfined Aquifer)
Sy = Volume of Water Drained / Total Volume of Aquifer
Hydrogeology
Aquifer Storativity (Confined Aquifer)
S = Ss * b
Hydrogeology
Well Drawdown (Thiem Equation, Confined Aquifer)
s = (Q / (2π*T)) * ln(R/r)
Hydrogeology
Hydraulic Conductivity from Intrinsic Permeability
K = (k * ρ * g) / μ
Hydrogeology
Groundwater Volumetric Flow Rate (Darcy's Law)
Q = K * A * (dh/dl)
Hydrogeology
Darcy's Law (Groundwater Flow Velocity)
v = -K * (dh/dl)
Seismology
Moment Magnitude Scale
Mw = (2/3)*log10(M0) - 10.7
Seismology
Seismic Moment
M0 = μ * A * D
Seismology
Fault Slip Rate
Slip Rate = Total Displacement / Time Elapsed
Seismology
Tsunami Wave Speed (Shallow Water Wave)
v = sqrt(g*h)
Seismology
Peak Ground Acceleration Attenuation (Simplified)
PGA = a * 10^(b*M) / (R+c)^d
Seismology
Earthquake Energy Release (Magnitude-Energy Relation)
log10(E) = 1.5*M + 4.8
Seismology
Seismic Wave Travel Time
t = D / v
Seismology
Earthquake Epicenter Distance (S-P Wave Time Interval)
D = (Vp * Vs / (Vp - Vs)) * (Ts - Tp)
Hydrogeology
Aquifer Transmissivity
T = Kb
Seismology
P-wave Velocity
V_p = √((K + 4μ/3) / ρ)
Seismology
Richter Magnitude Scale
M = log₁₀(A) − log₁₀(A₀)