geod quiz 4 - Sheet1 Flashcards
Who proposed the theory of rigid plates?
McKenzie and Parker
Who was one of the first people to determine the number of tectonic plates?
Le Pichon
What do we use now to determine the number of tectonic plates?
GEODVEL and MORVEL
What are the key ideas behind plate tectonics?
15 major plates, 56 plates in MORVEL56, plates are mostly rigid, deformation is essentially localized at plate boundaries
How does the oceanic crust provide key constraints for kinematics?
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
what gives us relative plate motion?
transform fault directions, sea-floor magnetic isochrons, and earthquake slip vectors.
What is an euler pole?
a pole of rotation (lat, long)
What describes the motion of plates on a sphere
an euler pole, an angular velocity (these are = to a 3 component angular rotation vector in a cartesian geocentric frame.
what is a forward problem vs an inverse problem?
forward = estimated parameters - model / theory - prediction of data. inverse = measured data - model/ theory - prediction of parameters
who developed the theory of elastic rebound?
harry reid (bc of san andreas fault triangulation network.
what is the elastic rebound theory?
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
what is the linear elastic system
the interseismic strain accumulation is the exact opposite of the coseismic strain release
when are interseismic plate motions faster?
away from locked faults ( and slower close to locked faults)
what drives postseismic deformation?
afterslip, poroelastic effects, viscoelastic relaxation in lower crust / upper mantle
how long can postseismic signals last?
hours to decades
what are episodic tremor and slip?
displacements not associated with large magnitude earthquakes (aseismic slip), observed at subduction zones
what are the interseismic, coseismic, and postseismic aspects of elastic rebound theory?
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
what is the difference between secular and transient deformation
secular = interseismic, constant, 1-10s of mya (LINEAR), transient = shorter time frames, non-tectonic processes (GIA, volcanos, post seismic), LOG or EXPONENTIAL
what causes volcanic deformation?
intrusions of magma in subsurface, removal of magma to the surface when erupting, pressure changes in hydrothermal systems
what are types of volcanic models?
mogi source, spherical, spheroid, ellipsoid, sill, dislocation.
what is there always a tradeoff of?
depth and source strength ( p or change in V)
what ctech can we use to detect landslides?
LiDAR, InSAR, DInSAR, GNSS
what is DInSAR
differential InSAR, used to identify footprints of progressing movement. use a DEM
what causes the most global sea level rise?
melting of glaciers and ice sheets
what do we use to observe VLM (vertical land motion)
InSAR, GNSS, InSAR + GNSS, VLM from tide gauges
what is the importance of VLM?
it’s a fundamental observable, allows us to measure impacts of SLR
what are the advances made in the field of geodesy in the last decade?
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
what are the grand challenges in geodesy over the past decade?
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?
what did grove karl gilbert do?
understood slip faults and earthquakes, suggested a rhythm of earthquakes and the seismic gap theory (earthquakes alternate positions along seismic zones)
what tech can we use for interseismic, coseismic, postseismic, and episodic tremor and slip aspects of earthquakes?
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)
what is PSI and what is it used for?
persistent scatter interferometry. landslide activity and intensity
