new observations in earth s normal modes of free oscillation n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
New Observations in Earth’s Normal Modes of Free Oscillation PowerPoint Presentation
Download Presentation
New Observations in Earth’s Normal Modes of Free Oscillation

Loading in 2 Seconds...

play fullscreen
1 / 26

New Observations in Earth’s Normal Modes of Free Oscillation - PowerPoint PPT Presentation


  • 142 Views
  • Uploaded on

New Observations in Earth’s Normal Modes of Free Oscillation. 趙丰 Benjamin F. Chao, 雷湘鄂 Xiang’E Lei 1 朱澄音 Amelie C. Chu, Institute of Earth Sciences, Academia Sinica , Taiwan 1 also at Inst. Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan. Normal modes ||.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'New Observations in Earth’s Normal Modes of Free Oscillation' - baka


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
new observations in earth s normal modes of free oscillation
New Observations in Earth’s Normal Modes of Free Oscillation

趙丰 Benjamin F.Chao,

雷湘鄂Xiang’E Lei1

朱澄音 Amelie C. Chu,

Institute of Earth Sciences, Academia Sinica, Taiwan

1also at Inst. Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan

slide2

Normal modes

||

Traveling-wave – Standing-wave

Equivalence

sin(wt + kx) + sin (wt – kx)

= 2 sinwt * coskx

slide4

(3-D) (discrete)

Eigenfunction , Eigenfrequency

nulm,nωlm

degree

overtone number

order

n=0: Fundamental modes ~ Surface waves

n>0: Overtone modes ~ Body waves

earthquake displacement field
Earthquake Displacement Field

• Equation of motion

• Solve by expanding displacement field

Normal mode eigenfunctions for SNREI Earth

Expansion coefficients (note the static limit)

(Gilbert, 1970 )

slide6

Deep Earthquakes:

1970 Colombia, M 8.0, depth = 650 km

1994 Bolivia, M 8.2, depth = 630 km

2013 Okhotsk Sea, M 8.3, depth = 609 km

slide7

Product power spectrum (logarithm)

V

~60 stations

H

~80 stations

slide8

Product power spectrum (logarithm)

V

~60 stations

H

~80 stations

slide9

Product power spectrum (logarithm)

V

~60 stations

H

~80 stations

slide10

Product power spectrum (logarithm)

V

~60 stations

H

~80 stations

slide11

Product power spectrum (logarithm)

V

~60 stations

H

~80 stations

slide13

GSI’s GNSS stations

  • GSI (Geospatial Information Authority of Japan)
    • GEONET(GNSS Earth Observation Network System)
  • Total 1230 stations at an average interval of about 20km for crustal deformation monitoring and GNSS surveys.
  • # Station used in this study: 1019

(http://dbx.cr.chiba-u.jp)

slide15

GPS Data Processing:

  • GIPSY/OASIS-II (Ver. 6.1)
  • Precise Point Positioning (PPP) technique
  • Sampling Rates: 30 sec.
  • Data Length: 21hrs (starts from 06:00 (UTC) 11th, March) 30hrs (starts from 18:00 (UTC) 11th, March)
  • We carry out simple spectral stacking, reducing the variance of the noise level
spectral stack gsi japan
Spectral Stack – GSI, Japan

0S2

0S3

0S4

0T2

|Y(f)|2

0S9

2T1

0T15

2T2

2T7

0T20

1T11

1T12

0T17

1T9

0S10

0T3

0T11

0T19

0T13

0T22

0T4

0T10

0T12

0T14

0T21

0T18

- - - fundamental toroidal modes

spectral stack gsi japan1
Spectral Stack – GSI, Japan

0S2

X

0S3

0S4

0S0

0T2

0S8

0S7

0S12

0S9

0S6

0S21

0S18

0S20

1S4

-: Fundamental spheroidal modes

pbo network
PBONetwork
  • The Plate Boundary Observatory (PBO) ofEarthScopemeasures Earth deformation through its arrays of GPS receivers, strainmeters, seismometers.
  • Ref. Frame: IGS08
  • # GPS Records: 1548
stack pbo western u s
Stack – PBO, Western U.S.

0S6

1S4

0S3

0S2

x

0S0

0S9

0S5

0T8

0S10

1S10

0S8

0T18

1S8

0T23

2T1

0T13

0T12

x

2T2

0T6

0S4

0T10

0T11

slide22

24 BPR records used (15 for 2010 Chile, 5 for 2011 Japan, 3 for 2005 Sumatra/Nias, 1 for 2004 Sumatra): After arrival of seismic waves but before tsunami, typically several hours long, at “event mode” 15-sec sampling.

slide24
Spectrum of a single DART (BPR21413) record

for 2010 Chile earthquake

Blue: pre-earthquake Red: during earthquake

Pink line: spheroidal 0Sn modesGreen line: toroidal 0Tn modes

slide25
Spectral Stack of 24 DART records for 4 earthquakes

Blue: pre-earthquake Red: during earthquake

Pink line: spheroidal 0Sn modesGreen line: toroidal 0Tn modes

what does ocean bpr record
What does ocean BPR record?
  • Assuming hydrostatic (OK for <60 mHz)
  • Pressure changes because the “g” in P=ρgHchanges, from g to g±a(equivalence principle), where a is the vertical acceleration associated with the given mode, or dω2 => spheroidal modes only? (but we see toroidal modes too…)
  • Additionally the dynamic drag produces an opposing pressure ½ CDρv2 which is tiny.