geod quiz 4 - Sheet1

Question 1

Who proposed the theory of rigid plates?

Answer 1

McKenzie and Parker

Question 2

Who was one of the first people to determine the number of tectonic plates?

Answer 2

Le Pichon

Question 3

What do we use now to determine the number of tectonic plates?

Answer 3

GEODVEL and MORVEL

Question 4

What are the key ideas behind plate tectonics?

Answer 4

15 major plates, 56 plates in MORVEL56, plates are mostly rigid, deformation is essentially localized at plate boundaries

Question 5

How does the oceanic crust provide key constraints for kinematics?

Answer 5

We use magnetic anomalies in the oceans (linear magnetic anomalies, parallel to ridges, symmetrical patterns at the ridges), provides spreading rates, transform faults can link spreading centers, also we can find the spreading direction

Question 6

what gives us relative plate motion?

Answer 6

transform fault directions, sea-floor magnetic isochrons, and earthquake slip vectors.

Question 7

What is an euler pole?

Answer 7

a pole of rotation (lat, long)

Question 8

What describes the motion of plates on a sphere

Answer 8

an euler pole, an angular velocity (these are = to a 3 component angular rotation vector in a cartesian geocentric frame.

Question 9

what is a forward problem vs an inverse problem?

Answer 9

forward = estimated parameters - model / theory - prediction of data. inverse = measured data - model/ theory - prediction of parameters

Question 10

who developed the theory of elastic rebound?

Answer 10

harry reid (bc of san andreas fault triangulation network.

Question 11

what is the elastic rebound theory?

Answer 11

between earthquakes, motion loads on the fault and strain accumulates near the fault. during earthquakes the fault breaks and slip of the fault catches up with displacements. ff

Question 12

what is the linear elastic system

Answer 12

the interseismic strain accumulation is the exact opposite of the coseismic strain release

Question 13

when are interseismic plate motions faster?

Answer 13

away from locked faults ( and slower close to locked faults)

Question 14

what drives postseismic deformation?

Answer 14

afterslip, poroelastic effects, viscoelastic relaxation in lower crust / upper mantle

Question 15

how long can postseismic signals last?

Answer 15

hours to decades

Question 16

what are episodic tremor and slip?

Answer 16

displacements not associated with large magnitude earthquakes (aseismic slip), observed at subduction zones

Question 17

what are the interseismic, coseismic, and postseismic aspects of elastic rebound theory?

Answer 17

inter = displacement at a given site is LINEAR and a function of time and constant velocity, co = jump in time series, related to mag and depth of earthquake, post = strain readjustments and decay related to lithospheric rheology

Question 18

what is the difference between secular and transient deformation

Answer 18

secular = interseismic, constant, 1-10s of mya (LINEAR), transient = shorter time frames, non-tectonic processes (GIA, volcanos, post seismic), LOG or EXPONENTIAL

Question 19

what causes volcanic deformation?

Answer 19

intrusions of magma in subsurface, removal of magma to the surface when erupting, pressure changes in hydrothermal systems

Question 20

what are types of volcanic models?

Answer 20

mogi source, spherical, spheroid, ellipsoid, sill, dislocation.

Question 21

what is there always a tradeoff of?

Answer 21

depth and source strength ( p or change in V)

Question 22

what ctech can we use to detect landslides?

Answer 22

LiDAR, InSAR, DInSAR, GNSS

Question 23

what is DInSAR

Answer 23

differential InSAR, used to identify footprints of progressing movement. use a DEM

Question 24

what causes the most global sea level rise?

Answer 24

melting of glaciers and ice sheets

Question 25

what do we use to observe VLM (vertical land motion)

Answer 25

InSAR, GNSS, InSAR + GNSS, VLM from tide gauges

Question 26

what is the importance of VLM?

Answer 26

it’s a fundamental observable, allows us to measure impacts of SLR

Question 27

what are the advances made in the field of geodesy in the last decade?

Answer 27

studying the ice sheets, discovering aseismic slip in subduction zones, measuring secular and transient deformation, studying global SLR, studying magma activity and volcanoes, establishing international geodetic organizations, establishment of earthscope

Question 28

what are the grand challenges in geodesy over the past decade?

Answer 28

will humanity have enough water to sustain itself, how will SLR affect earth, how do glaciers change from months to centuries, how do tectonic plates deform, what processes control earthquakes, how does earth’s surface evolve, what are the mechanics of magmatic systems?

Question 29

what did grove karl gilbert do?

Answer 29

understood slip faults and earthquakes, suggested a rhythm of earthquakes and the seismic gap theory (earthquakes alternate positions along seismic zones)

Question 30

what tech can we use for interseismic, coseismic, postseismic, and episodic tremor and slip aspects of earthquakes?

Answer 30

inter= GNSS/GPS and InSAR IF large enough, coseismic= InSAR, post=GNSS and InSAR IF large enough, episodic temor and slip= GNSS (too small and sparse for InSAR)

Question 31

what is PSI and what is it used for?

Answer 31

persistent scatter interferometry. landslide activity and intensity