# Interval velocities

Series | Geophysical References Series |
---|---|

Title | Problems in Exploration Seismology and their Solutions |

Author | Lloyd P. Geldart and Robert E. Sheriff |

Chapter | 5 |

Pages | 141 - 180 |

DOI | http://dx.doi.org/10.1190/1.9781560801733 |

ISBN | ISBN 9781560801153 |

Store | SEG Online Store |

## Contents

## Problem 5.15

An survey gives the stacking velocity results in Table 5.15a. Calculate the interval velocities.

1 | 1.20 | 1.100 | 2.18 |

2 | 2.50 | 1.786 | 2.80 |

3 | 3.10 | 1.935 | 3.20 |

4 | 4.10 | 2.250 | 3.64 |

### Background

In equation (4.13a), the sum is the traveltime down to the base of the layer, that is, . Therefore equation (4.13a) can be written

**(**)

If we write and for the rms velocity and traveltime down to the base of the layer, and for the same quantities down to the top of the layer, we can get an equation for the interval velocity in the bed by subtracting expressions for and obtained from equation (5.15a). The result is

**(**)

### Solution

We assume horizontal velocity layering so that the values of in Table 5.15a are approximate values of (see Table 5.12b) and therefore we can use equation (5.15b) to find interval velocities. We take 2.18 km/s as the interval velocity from the surface to the first reflector. We now calculate the interval velocities to :

## Continue reading

Previous section | Next section |
---|---|

Well-velocity survey | Finding velocity |

Previous chapter | Next chapter |

Geometry of seismic waves | Characteristics of seismic events |

## Also in this chapter

- Maximum porosity versus depth
- Relation between lithology and seismic velocities
- Porosities, velocities, and densities of rocks
- Velocities in limestone and sandstone
- Dependence of velocity-depth curves on geology
- Effect of burial history on velocity
- Determining lithology from well-velocity surveys
- Reflectivity versus water saturation
- Effect of overpressure
- Effects of weathered layer (LVL) and permafrost
- Horizontal component of head waves
- Stacking velocity versus rms and average velocities
- Quick-look velocity analysis and effects of errors
- Well-velocity survey
- Interval velocities
- Finding velocity
- Effect of timing errors on stacking velocity, depth, and dip
- Estimating lithology from stacking velocity
- Velocity versus depth from sonobuoy data
- Influence of direction on velocity analyses
- Effect of time picks, NMO stretch, and datum choice on stacking velocity