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Seismic Distance Equation:
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The Lag Time To Distance calculation determines the seismic distance from the time difference between P-wave and S-wave arrivals. This is a fundamental calculation in seismology used to locate earthquake epicenters.
The calculator uses the seismic distance equation:
Where:
Explanation: The equation calculates the distance to an earthquake epicenter based on the time difference between the faster P-waves and slower S-waves, using known seismic wave velocities.
Details: Accurate distance calculation is crucial for earthquake location, determining epicenter coordinates, and assessing seismic hazard. It forms the basis for triangulation methods used to pinpoint earthquake locations.
Tips: Enter lag time in seconds, P-wave velocity in km/s, and S-wave velocity in km/s. All values must be positive, and Vp must be greater than Vs for valid results.
Q1: What is lag time in seismology?
A: Lag time refers to the time difference between the arrival of P-waves (primary waves) and S-waves (secondary waves) at a seismic station.
Q2: Why must Vp be greater than Vs?
A: P-waves always travel faster than S-waves through the same medium, so Vp must be greater than Vs for the calculation to be physically meaningful.
Q3: What are typical values for Vp and Vs?
A: In continental crust, Vp is typically 5-7 km/s and Vs is 3-4 km/s. These values vary with rock type and depth.
Q4: How accurate is this distance calculation?
A: Accuracy depends on the precision of the lag time measurement and the accuracy of the velocity model used for the specific region.
Q5: Can this be used for earthquake early warning systems?
A: Yes, the lag time method is fundamental to many earthquake early warning systems that estimate distance and magnitude from initial seismic wave arrivals.