69716 - Laboratory of Geophysics 2

Learning outcomes

At the end of the course, students will possess technical and practical know-how on some of the main experimental methods of investigation used in Geophysics. as well as the theoretical ground on which the methods are based. Particularly, students will be able to perform shallow surface geophysical prospecting with seismic refraction techniques as well as seismic reflection techniques.

 

Course contents

The course is composed of two modules.

Module 1 (Prof. Filippo Zaniboni):

1. General introduction to seismic waves: P waves, S waves, plain and inhomogeneous waves, Rayleigh waves, Love waves.

2. Seismic waves attenuation: quality factor, gain and attenuation unity of measure, P and S waves attenuation.

3. Refracted waves: reflection and transmission coefficients across an interface, impedance, critical angle, reflection and transmission of P and S waves, source method.

4. Crustal seismic waves: active and passive seismics, direct, reflected and refracted wave dromochrones.

5. Refraction seismics: seismic prospection, crossover distance, horizontal interface dromochrone, dipping interface dromochrone, direct and conjugate path, delay time method, phantom arrivals, multi-layer seismics and anomalous cases, Palmer method (GRM).

Planning a seismic refraction survey.

Lab exercises related to refraction seismics on data provided by the teacher and collected in the field.

 

Module 2 (Prof. Alberto Armigliato): Reflection seismics.

1. Dromochrone for a wave reflected by a single plane interface. Reflection hyperbola. Normal-Move-Out (NMO) correction. Reflected waves in a multilayer medium with parallel interfaces: Dix's formula. Reflection from a single dipping interface - dip move-out.
2. Surveying strategies and acquisition configurations. Types of gathers, with special emphasis on the Common Mid Point gathers.
3. Velocity analysis. Stacking and time section. 
4. Basics on filters.
5. Basics on migration.
6. Lab exercises related to reflection seismics on data provided by the teacher and collected by the students in the field.

 

Readings/Bibliography

Slides and lecture notes, available online at https://virtuale.unibo.it/.

 

The following textbooks can be useful:

H. Robert Burger, Anne F. Sheehan, Craig. H. Jones. Introduction to Applied Geophysics: Exploring The Shallow Subsurface, Norton, 2006.

John M. Reynolds, An introduction to Applied and Environmental Geophysics, 2nd Edition, Wiley, 2011.

Yilmaz, Seismic Data Analysis. Available online athttps://wiki.seg.org/wiki/Seismic_Data_Analysis

Teaching methods

Classroom lectures and experiments carried out in the laboratory and field survey.

The attendance of the lessons in the classroom is not compulsory, but it is highly recommended for the learning process and for its tight connection to the lab experiences.

The laboratory and field experiments are compulsory: the lecturers will collect the students' signatures at the beginning of each turn.

 

As concerns the teaching methods of this course unit, all students must attend in advance

- Module 1, 2 of the formation course on health and safety (to be attended online)

- Module 3 in presence, based on a schedule that will be timely announced by the Department of Physics and Astronomy.

For further information, please consult the web site: https://site.unibo.it/tutela-promozione-salute-sicurezza/it/corsi-di-formazione/formazione-obbligatoria-su-sicurezza-e-salute-per-svolgimento-di-tirocinio-tesi-laboratorio

 

Assessment methods

At the end of the laboratory activities, students must complete two separate written reports for

• the refraction seismics
• the reflection seismics.

The reports must be delivered and sent to the lecturers no later than 15 days after the end of the course, and anyway before the exam.

The reports will not get a separate mark, but the discussion on them will be part of the exam.

The final test has the aim of ascertaining that the formation objectives are achieved and consists of a single oral examination, concerning theory as well as the experimental tests carried out in the laboratory and in the field.

The typical exam duration is between one hour and one hour and a half.

Teaching tools

In the room: projector.

In the lab:

· two PCs with free and commercial software for data modelling and visualization;

In the field:

- Geode 24 channles seismometer with accessories, geophones, seismic hammer, minibang.

 

Students with DSA or temporary or permanent disabilities: it is recommended to contact the responsible University office in good time (https://site.unibo.it/studenti-con-disabilita-e-dsa/it): it will be their responsibility to propose any adaptations to the students concerned, which must however be submitted, 15 days in advance, to the approval of the teacher, who will evaluate the opportunity also in relation to the educational objectives of the course.

 

Office hours

See the website of Alberto Armigliato

See the website of Filippo Zaniboni