PAG Activity 2.01 AS and a Level Geology

Geology PAG 2: Investigating seismology

Suggested Activity 1: Using a seismic database

Instructions for teachers & technicians

This practical activity is composed of two parts; a teacher/technician section and the student activity which can be found on page 7. This practical activity supports OCR AS/A Level Geology.

When distributing the activity section to the students either as a printed copy or as a Word file you will need to remove the teacher instructions section.

OCR recommendations:

Before carrying out any experiment or demonstration based on this guidance, it is the responsibility of teachers to ensure that they have undertaken a risk assessment in accordance with their employer’s requirements, making use of up-to-date information and taking account of their own particular circumstances. Any local rules or restrictions issued by the employer must always be followed.

CLEAPSS resources are useful for carrying out risk-assessments: ().

Centres should trial experiments in advance of giving them to students. Centres may choose to make adaptations to this practical activity, but should be aware that this may affect the Apparatus and Techniques covered by the student.

This document may have been modified – if in doubt check the master version on OCR Interchange.

Version 1.0 – August 20171© OCR 2017

Introduction

Students will search the ANSS Comprehensive Earthquake Catalog (ComCat) and compile a user defined dataset which they will export to a Geographical Information System (Google Earth or ArcGis). Within the GIS environment they will display their data to optimise the visualisation (show in a way that emphasises underlying patterns) of the relationship between spatial distribution and depth to focus of earthquake data at a convergent plate boundary. Finally they will abstract a subset of their data for further analysis. A common misconception is that GIS essentially is a display system for existing maps; like an electronic version of the thematic maps in a school atlas. The activity allows students to start to explore the functionality of GIS.

Aims

• to compile a user defined geological data set from the ANSS ComCat
• to use a GIS to analyse, interrogate and visualise their geological data set
• to tabulate and graph their data in a scientific way.

Intended class time

• 1 hour

Practical Skills – competence assessed by the teacher

1.2.1 (b) safely and correctly use a range of practical equipment and materials

1.2.1 (c) follow written instructions

1.2.1 (d) make and record observations/measurements

1.2.1 (f) present information and data in a scientific way

1.2.1 (g) use appropriate software and tools to process data, carry out research and report findings

1.2.1 (j) use a wide range of experimental and practical instruments, equipment and techniques

appropriate to the knowledge and understanding included in the specification.

1.2.2 (m)(ii) use of ICT to: compile and analyse geological data sets to enable visualisation using geographic information system (GIS)

CPAC – competence assessed by the teacher

(1) follows written procedures

(2) applies investigative approaches and methods when using instruments and equipment

(4) makes and records observations.

(5) researches, references and reports

Links to Specifications

3.2.1 (b)(i) the evidence from earthquake seismology data for the nature of lithospheric plates (aseismic interiors and margins defined by seismic activity)

3.2.1 (c) the nature of lithospheric plates: aseismic interiors and margins defined by seismic activity

3.2.1 (g) subduction zones, lithospheric plates (cold thermal boundary) and mantle plumes which act as the active limbs of the convection cells which transfer energy from within the Earth

3.2.1 (i) the relative importance of slab pull at subduction zones and ridge push at mid-ocean ridges as mechanisms driving the movement of tectonic plates

3.3.2 (c) how plate movement at convergent plate margins causes compressive and shear dominated tectonic environments, which can lead to rock deformation as a result of tectonic or gravity induced stresses

6.1.1 (a) the factors which affect the impact of earthquakes

Mathematical Skills – learning opportunity within activity

• Mathematical skills must be applied in the recording of the data and calculations, and in analysing the data. These steps require the appropriate application of the following mathematical skills:
• M1.1Recognise and make use of appropriate units in calculations.
• M1.3Use an appropriate number of significant figures.
• M2.2Construct and interpret frequency tables and diagrams, bar charts and histograms.
• M2.9Plot two variables from experimental or other linear data.
• M2.10Use a scatter diagram to identify a correlation between two variables
• M3.7Translate information between graphical, numerical and algebraic forms
• M4.2Visualize and represent 2D and 3D forms, including 2D representations of 3D objects

Equipment

Each student will require:

• computer with Google Earth (or ArcGIS) application installed and internet access
• A4 graph paper with 2 mm grid lines

Health and Safety

• Health and safety should always be considered by a centre before undertaking any practical work. A full risk assessment of any activity should be undertaken including checking the CLEAPSS website (

Notes

Centres are advised to trial this activity before using it with students. In particular:

• in order to use .KML files , you will need to install Google Earth or Google My Maps.
• an alternative is to use esri ArcGIS which is free to schools schools.esriuk.com/
• this activity has been adapted with permission of the author from a workshop demonstration at ESTA 2016, University of St Andrews. Pete Loader 2017, Google Tectonics, Teaching Earth Sciences Vol 42, No 1.

Answers and Guidance to Extension Activities

1. An example from the Nazca plate is given below. Students need to consider how representative their data is as frequent small shallow events may mask deeper events associated with the Benioff zone.
2. At a convergent boundary the subducting slab will form a curved not a planar upper surface. Other complexities may include tears and more complex large scale folds.
3. Small events (<5M) are only recorded when there is a good seismograph network while larger events have more records and are better constrained. Dates will be accurate but differences in data format could introduce errors (i.e. YYYY.MM.DD v DD.MM.YYYY) Distances using ruler tool are probably 2 × ±10 km. Depths (especially shallow depths often cluster (e.g. 33 km).
4. The worldwide seismic network allowed geologists to identify that most seismic activity is concentrated in narrow zones which define the boundaries of the tectonic plates based on 1961-1967 seismic records (e.g. Isaks, B. & Oliver, J. 1968 Seismology and the New Global Tectonic, JGR 73, pp 5855-5899)

1. The most comprehensive coverage is within the contiguous USA where data on events down to M2.0 may be available. Elsewhere on ‘significant’ events less than M5.0 are recorded and this may vary with the density of the local seismograph network. Magnitudes and locations are also subject to revision for several months after an event. Care needs to be taken when using secondary data as units and formats vary and derived measurements (like Magnitude) may have varying definitions. In the case of NASA’s Mars Climate Orbiter thrust data was supplied in lbf (pounds force) not Newtons (1 lbf = 4.45 N) causing it to crash into Mars rather than entering into orbit in September 1999. The huge and growing volume of big data (while it may be unstructured and inconsistent) allows Earth scientists to investigate issues (like earthquake prediction and climate change).

Records

As evidence for the Practical Endorsement, students:

• should not need to re-draft their work, but rather keep all of their notes as a continuing record of their practical work, dating their work clearly,
• should print a screen grab of their GIS data visualisation
• should record any measurements taken to the number of decimal places (resolution) appropriate. This should be recorded clearly in a table format with appropriate units,
• should use the data collected to a plot graph and draw conclusions

Extension questions help students develop their understanding of the underlying geological theory and are a preparation for the written examinations. They also help students to develop the practical science skills assessed indirectly in the written examinations and they should be encouraged to record their data appropriately, for example showing full workings in calculations, and stating final answers to the appropriate number of significant figures.

Document updates

v1.0August 2017Original version.

Example scatterplot produced from analysis of ComCat

The ANSS ComCat contains a comprehensive database of global seismic events greater than Magnitude 5.0 from the mid 1970s. Historical and lower magnitude data is available for but this is not complete. The size of the data base means that students must select a subset of data to export to the GIS.

https://earthquake.usgs.gov/earthquakes/search/

Google Earth uses KML files and ArcGIS CSV files. Appropriate display characteristics need to be selected for the data to be usable.

The measuring tool in Google Earth (or ArcGIS) can be used to measure the distance on the ground from the trench axis to the epicentre. At this scale the distortions on areas and distances produced by projecting the spheroid onto a flat surface introduce errors if simply measured off the screen without using the GIS tool. Note that additional attributes can be displayed for all data points using the query menus. ArcGIS has additional ‘mapamatical’ functionality which could be explored by students in PAG11 or PAG12.

This document may have been modified – if in doubt check the master version on OCR Interchange.

Version 1.0 – August 20171© OCR 2017

Geology PAG 2: Investigating seismology

Suggested Activity 1: Using a seismic database

Student activity

Introduction

In this practical activity you will search the ANSS Comprehensive Earthquake Catalog (ComCat) and compile a user defined dataset which you will export to a Geographical Information System (Google Earth or ArcGis). Within the GIS environment you will display your data to optimise the visualisation of the relationship between spatial distribution and depth to focus of earthquakes at a convergent plate boundary. Finally you will abstract a subset of your data for further analysis.

You are expected to be familiar with the basic principles of plate tectonics and have some understanding of convergent plate boundaries and subduction zones.

You will have to select appropriate units and other parameters from a database which may have unfamiliar units as default (i.e. imperial units, US data format). You will be producing a data table and a graph. You will be expected to use standard scientific practice including adding annotations and a scale bar to your drawing(s).

Aims

• to compile a user defined geological data set from the ANSS ComCat
• to use a GIS to analyse, interrogate and visualise their geological data set
• to tabulate and graph their data in a scientific way.

Intended class time

1 hour

Equipment

computer with Google Earth application installed and internet access

graph paper

Health and Safety

• You should follow your centre’s practice on using computers and the internet.

This document may have been modified – if in doubt check the master version on OCR Interchange.

Version 1.0 – August 20171© OCR 2017

Procedure

Before starting your practical work, read the information below.

1. Go to the USGS Earthquake Hazard Program website (earthquake.usgs.gov/earthquakes) and select ‘Search Earthquake Catalog' to access the ANSS ComCat.
2. Search for: >Magnitude 5, a time period of at least 20 years and a custom area based on any subduction zone that you choose. Set your output options to: KML format, colour by depth and largest magnitude first. [If you are using ArcGIS you will have to choose CSV format.]
3. With Google Earth open when you click on the query.kml file it will open in Google Earth. [If you are using ArcGIS then just drag and drop the query.csv file onto the ArcGIS map].
4. Using the cursor and ruler tool [or ] compile and tabulate data on 15 earthquakes representing a range of distances from the axis of the oceanic trench. You should measure the distance perpendicular to the trench axis. For each event you will need record: magnitude, date, distance of the epicentre from the oceanic trench axis and the depth to the focus.
5. Make a record of your work such as by taking a screen grab of the GIS display and print it.
6. Produce a scattergraph to show the relationship between distance from the oceanic trench axis and the depth to focus.

Extension opportunities

1. Describe the pattern you have observed and suggest why it occurs; you may wish to annotate you graph with your conclusions.
2. What are the advantages and disadvantages of the GIS display and your scatterplot in showing the pattern of seismicity in the subduction zone?
3. What are the sources of error in your measurements? Make an attempt at quantifying the uncertainties in your tabulated data.
4. The worldwide seismograph network was started in 1961 to monitor a nuclear test ban treaty. Earthquakes and nuclear explosions have different seismograph signatures (nuclear explosions show no strike slip motion). Suggest why this seismic network was important in establishing plate tectonics in the late 1960s and early 1970s.

1. (a) The ANSS ComCat is an example of big data. Read the ‘ComCat Documentation – Data Availability’ page (earthquake.usgs.gov/data/comcat/data-availability.php). How comprehensive is ANSS ComCat and how does the data coverage vary?

(b) Did you have any issues with the units or formatting of data in ANSS ComCat? What recommendations would you suggest for the use of units in an international science project, and why? (You may wish to research NASA’s Mars Climate Obiter mission.)

(c) Given the issues of coverage and data volume (which make it impossible to process ‘big data’ on a single computer) why do geologists and other scientist want to use ‘big data’?

Records

As evidence for the Practical Endorsement, you need records of:

• the screen grab of your GIS data visualisation,
• a table of abstracted data, with appropriate units
• a scattergraph of the relative positions of the focuses of the earthquakes.

All work should be clearly dated.

In addition you should have considered the above questions as the answers to these questions will aid you in preparation for your written examinations.

This document may have been modified – if in doubt check the master version on OCR Interchange.

Version 1.0 – May 20171© OCR 2017