Stanford University, CA December 9-12, 2004 Northeast Russia Tectonics Workshop1 Tectonic Plates in Northeast Asia: GPS Evidence 1 RDAAC/Geophysical Service

Stanford University, CA December 9-12, 2004

Northeast Russia Tectonics Workshop

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Tectonic Plates in Northeast Asia: Tectonic Plates in Northeast Asia: GPS EvidenceGPS Evidence

1 RDAAC/Geophysical Service RAS, Moscow, Russia2 Lamont-Doherty Earth Observatory of Columbia University, USA3 IMGG FEB RAS, Yuzhno-Sakhalinsk, Russia4 KOMSP Geophysical Service RAS, Petropavlovsk, Russia5 MIT, Cambridge, MA, USA6 University of California Berkeley, USA7 Institute of Physics and Technology RAS, St Petersburg, Russia

Contributed:

Nikolai F. Vasilenko3

Vasily Y. Levin4

Robert W. King5

Thomas A. Herring5, Christopher H. Scholz2, Roland Bürgmann6

Dmitry I. FrolovDmitry I. Frolov77

Grigory M. SteblovGrigory M. Steblov11, , Mikhail G. Mikhail G. KoganKogan22



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Plate Scenarios for East Asia

• Geometry of the Eurasia – North America plate boundary in east Asia has been discussed since the 1970s, with varying interpretations of diffuse seismic belts in Siberia and marginal seas.

GPS observations in Siberia in 1996-2004, combined with global observations, place crucial constraints on the plate scenario for east Asia.



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Network used in Solution GPS2004.9

• GPS2004.9 is a global solution with a focus on sampling the stations in Siberia. These stations represent both EUR and NAM. Epochs span 1996-2004.9



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Subset Sampling Stable Plate Interior

• Plates EUR, NAM, and PAC are sampled from three sources of GPS data:– Continuous and survey mode observations in eastern Russia under project RUSEG

since 1995– Continuous observations of the IGS Network– Continuous observations in western Pacific under project WING [Kato et al., 1998].



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Origin Translation Rate and Reference Frames• We evaluate the

reference frame (RF) origin translation rate from GPS data themselves for both components:– Along spin axis– Across spin axis

• As a result, the solution is independent of any conventional RF.



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Relative Motion EUR-NAM: Continuous Stations• By comparing velocities

relative to EUR



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Relative Motion EUR-NAM: Continuous Stations• By comparing velocities

relative to EUR and to NAM, we conclude that east Siberia to the east of the Cherskiy Range belongs to NAM. This geometry was hypothesized for three decades but never proven.



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Relative Motion EUR-NAM: Regional Surveys• Our scenario is further

confirmed by regional GPS surveys. Compare velocities over the Cherskiy Range, in Chukotka, and northern Kamchatka

–relative to

EUR



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Relative Motion EUR-NAM: Regional Surveys• Our scenario is further

confirmed by regional GPS surveys. Compare velocities over the Cherskiy Range, in Chukotka, and northern Kamchatka:

– and relative to

NAM



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Relative Motion EUR-NAM: Regional Surveys• Convergence rate EUR-NAM

is higher in Sakhalin than in Siberia for geometrical reasons.

• Sakhalin is a complex, seismically highly active deformation zone jammed between EUR and NAM.

• Predominant deformation style in Sakhalin is transpression, with the compressional component more conspicuous than the strike-slip.

EUR

NAM



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Amurian Microplate?• From GPS evidence, the

region attributed to “AMU” is, in fact, a mozaic of:– Zone of distributed

deformation in east China– Southern margin of

Siberian craton– Baikal Rift zone– EUR-NAM plate boundary

in Sakhalin

GPS Velocity Solutions: Steblov et al. [GRL, 2003]; Rotated and Translated to Steblov et al.: Zhang et al. [Geology, 2004]; Calais et al. [JGR, 2003]



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GPS and Geologic Plate Models

• For EUR-NAM, a comparison of GPS with NUVEL-1A shows– More rapid opening in

North Atlantic– More rapid EUR-NAM

convergence in east Asia

We found a significant discrepancy between geologic (NUVEL-1A) and geodetic relative plate motions for almost all plate pairs that were analyzed.



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Motion of Siberia vs Europe ?

• There are small, at a 1 mm/yr level, coherent plate-residual station velocities in Eurasia. They may reflect, if confirmed, a small relative motion of Europe and Siberia which were separate continents prior to collision along the Urals orogeny (in the Devonian).



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Motion of Siberia vs Europe ?• EUR-NAM rotation pole

is displaced to NW if GPS in Europe only is used [Steblov et al., 2003].

• Both NUVEL1-A and revised geologic plate model [Calais et al., 2003] give the pole location significantly different from GPS.



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Conclusions• GPS observations in east Siberia, combined

with global observations collected in 1995-2003, place constraints on the geometry and motion of Eurasian, North American, and Pacific plates in east Asia.

• From GPS evidence, easternmost Siberia to the E of the Cherskiy Range, including Chukotka and Kamchatka, belongs to the North American plate. The data do not invoke the presence of microplates here.

• GPS hints at a slight relative motion of Europe with respect to Siberia <2 mm/yr.



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Origin Translation Rate and Reference Frames• Geodetic solution yields well-

constrained interstation baselines Dij and their rates-of-change dDij/dt but not yet station velocities.

• The solution matrix is free to rotate and and “almost free” to translate (it is rank-deficient).

• Can we map dDij/dt into station velocities on several plates simultaneously?

• Yes, if the origin of reference frame has zero translation rate.



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Origin Translation Rate and Reference Frames• We evaluate the origin

translation rate (OTR) from GPS data themselves for both components:– Along spin axis



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Processing of GPS2004.0• At all steps of processing

except the last, station positions were loosely constrained.

• Definition of the Reference Frame is made consistently at the end in order to tightly constrain the solution for positions, velocities, and plate model.



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Origin Translation Rate and Reference Frames

• For GPS2004.0, origin translation rate is determined uniquely, regardless of the reference frame used.

• Rotation rates differ significantly; however, they cannot not affect relative plate rotation vectors.

• GPS2004.0 differs from ITRF2000_rfwg in origin translation rate by less than 0.5 mm/yr.

Transformation of Solution GPS2004.0 to Best-Fit ITRF2000_rfwg

RMS fit for 114 components from 57 stations: 0.79 mm/yr, NRMS: 0.76

Translation Rate Rotation rate Reference Frame for GPS2004.0

X Y Z X Y Z

mm/yr mm/yr mm/yr mas/yr mas/yr mas/yr

ITRF2000 0.23 ±0.15 0.18 ±0.15 0.16 ±0.15 -0.002 ±0.005 -0.003 ±0.005 0.005 ±0.005

A priori 0 mm/yr

0.23 ±0.15 0.18 ±0.15 0.16 ±0.15 0.156 ±0.005 0.437 ±0.005 0.153 ±0.005



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Discrepancy: GPS-Geology

• For all plates, GPS rms plate-residual velocities are much smaller than GPS-geologic differences.

NNR



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Origin Translation Rate and Reference Frames• A remarkable property

of our solution: it does NOT depend on a choice of Reference Frame (RF).

• 2 quite different RF were tested: – ITRF2000– A priori station velocities

set to 0

• Relative plate rotation vectors are identical in both cases.



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Micro-plates in east Asia ?

• GPS arguments for AMU were based on biased velocity of the single reference station (Tsukuba).

• RMS “plate-residual” velocity for AMU is as high as 2.5 mm/yr!



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Motion of Siberia vs Europe ?• All estimates dominated by

stations in Europe agree in more north-westerly location of pole EUR-NAM.

• Geologic plate models determine relative velocity of EUR and NAM mostly from marine magnetic anomalies in north Atlantic and in the Arctic. This is the motion of Europe relative NAM.



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Micro-plates in east Asia ?• South

Documents

Stanford University, CA December 9-12, 2004 Northeast Russia Tectonics Workshop1 Tectonic Plates in Northeast Asia: GPS Evidence 1 RDAAC/Geophysical Service