Geology 3120 The Scientific Method and Models

1
Geology 3120 - The Scientific Method and Models

• Nonconformity Contact corner on Flagstaff Mtn

2
The Scientific Method

• Identify the problem
• Research and evaluate
• Develop a multiple working hypothesis
• Challenge the hypothesis
• Modify the hypothesis or experiment

3
1. Identify the problem

• Personal discovery or a request by another
• Ask the key question!
• Identify resources
• Formulate a plan

4
2. Research and evaluate

• Literature review
• Empirical data (stuff we can see, existing
  examples)
• Theoretical modeling

5
3. Develop a multiple working hypothesis

• A hypothesis is a general statement and an idea
  that has not yet been proven
• If faced with data that could be explained with
  several ideas, formulate a multiple working
  hypothesis so you do not force a conclusion
• Ideas are like children, youre not supposed to
  favor one above another!

6
4. Challenge the hypothesis

• If the hypothesis is correct, your problem can
  be solved
• A hypothesis must be designed to be tested
• For a multiple working hypothesis, many aspects
  of interdisciplinary earth science may be
  explored/tested
• Use empirical or observational data to challenge
  the hypothesis
• Untestable hypotheses dont constitute science!

7
5. Modify the hypothesis or experiment

• If the hypothesis is not correct, consider
  modifying the hypothesis
• Should the experiment be modified?
• Should additional data be collected?
• Be prepared to create a hypothesis that was not
  expected

8
Example - The Journeys of Columbus
Formulating a Problem An Alternate Trade Route
to the Orient Hypothesis The world is a sphere
and that by sailing West one could reach the East
and establish a new trade route for Spain and
Europe. Objectives To sail West and plot a new
route to compare the new route to old routes to
collect goods from the Far East and return to
Spain Challenge of the Hypothesis The East was
not reached the New World was discovered
goods were returned to Spain
9
Models

• Geometric
• Kinematic
• Dynamic (Mechanical)

10
Geometric Models

• Interpretation of geologic structures in 2-D and
  3-D
• Useful data - geological mapping, geophysical
  surveys
• Common geometric models - maps, cross-sections,
  block diagrams, movies

Geologic cross-section, Kolob Canyons, Zion
National Park
11
Kinematic Models

• Specific history of motion from the undeformed
  state to the deformed state
• No consideration of physical properties or
  driving forces of motion
• Plate Tectonics is a good example of a kinematic
  model

Kinematic cross-section of faulting
12
Dynamic (Mechanical) Models

• Deformation is a function of the physical
  conditions and mechanical properties of the model

Numerical model of the interaction between a
mantle plume and spreading ridge
13
Group exercise
In groups of four, develop a hypothesis related
to some aspect of earth science.

• Identify the problem
• Ask the key question
• Research and evaluate
• Develop a multiple working hypothesis
• Challenge the hypothesis
• Modify the hypothesis or experiment

If time permits, we will share some of the
hypotheses with the class.
14
The interdisciplinary nature of modern Earth
Science
As a research geologist, I use many types of
data Making maps traditional mapping, airborne
and space photography, digital elevation data
(USGS, SRTM) for shaded relief, slope and
curvature maps, GPS (for locating contacts),
INSAR data for mapping ground movement For
making cross sections Traditional map data,
measurements in the field, GPS (regional
velocities), seismic reflection profiles, oil and
geotechnical boreholes (bucket auger CPT),
earthquake seismicity, trench excavations For
making models, I use mostly computer programs, 3D
visualization, Coulomb (stress calculations),
Trishear and Forced Fold (determining fault
geometries from fold shapes). My students also
use Matlab, ArcGIS, and code for processing
images and managing diverse databases.
15
New Madrid Short-lived intraplate folding in a
dextral restraining bend Big earthquakes (Mw
7.4) 2-3m slip _at_600 yr interval AD 1811, 1450,
900, 300 Little total uplift (50 m) Aftershocks
from 1811 Miss. River Floodplain Loess Uplands
16

• Surface deformation
• occurs mostly by subtle folding
• Most uplift
• occurs above thrust
• Only portion of fold preserved

Reelfoot
fold scarp
Floodplain
Lake
Uplands
Cottonwood Grove fault
17

• Topographic relief in NMSZ is
• subtle (lt5 -8 m on floodplain)

Topo Profile
Uplift
Reelfoot scarp Forelimb of fold
River
Lake
Basin
New Madrid Shaded Relief
18

• 9m uplift in 2300 yrs (slip rate 4.01.0
  mm/yr)
• 4-5 m of slip per event (every 600 years)
• 3 surface fold scarps suggests strain is
  distributed
• unevenly in forelimb, records heterogeneous
  shear
• Secondary extensional strain, no flexural slip
  faults
• No long-term record of growth strata
• Longer-term variation in slip rate is undefined
• Dont know why it turns on _at_ 15 ka

Trench Log across Reelfoot Scarp
19

• High-resolution seismic
• (Sexton Jones, 1986)
• fault propagation fold
• reflectors flatten upward
• fault offset at 0.6sec
• no growth strata

20
Simple Trishear Model

• Undertake structural
• analysis to determine
• dip of fault (i.e. to
• determine slip rate)
• restores strata
• defines fault dip (75o)
• estimates propagation
• of fault tip relative to
• fault slip (PS 9.0)
• determines that
• fault is reactivated

21
Downtown Osaka
Now lets move to Japan
Kuwana Anticline
Uemachi Upland/Fold
22
3D image of uppermost surfaces folded by Uemachi
Flexure
Top Ma-13
Base Ma-13
Top Ma-12
Note progressive increase in relief across
forelimb
Base Ma-12
Well data from Geo-Research Institute, Osaka
23
Uemachi S-wave profile
Note resolution of data (some reflectors at 1 m
spacing) Reflectors steepen downward Angular
unconformity from Holocene sea level highstand
Depth in meters
00
00
-10
-10
-20
-20
-30
-30
-40
-40
-50
-50
-60
-60
24
Uemachi S-wave profile plus borings
Only negative impedence shown
25
Uemachi S-wave profile line tracing
Note upwardly narrowing trishear envelope
26
Uemachi line tracing interpretation
Note flexural slip faults that terminate as
parasitic folds beneath unconformity Some of this
strain may postdate deposition of younger
strata Backfilling occurs above flexural slip
folds
27
Osaka Bay
Osaka Bay Flexure
28
Dip profile of forelimb of Osaka Bay FPF/blind
thrust
Most of reflectors are growth strata 1.5-2.0 km
of sediment fill in the last 1800 ka Note
homogeneous shear in forelimb
29
Dip profile of forelimb of Osaka Bay FPF/blind
thrust
Best fit trishear solution yields steep (74 deg)
thrust, 12km upward propagation (Fault tip from
15-gt3km) 10 deg apical angle