Geodetic monitoring of the Changbaishan volcano activity and its relationship with earthquakes,1999-2017

The major earthquakes often trigger unrest of surrounding volcanic magma chambers.In recent years,three major earthquakes occurred around the Changbaishan volcano,but it was unclear whether these earthquakes triggered the unrest of the magma chamber.Based on geodetic data,we analyzed the volcanic activity according to the Global Position System(GPS)and leveling sites time-series and reestimated the location and volume change of magma chamber from 2002 to 2005.Meanwhile,we calculated the dilatational strain variations of the deep magma chamber resulting from coseismic deformations caused by the 1999 Mw7.0 and 2002 Mw7.3 Wangqing deep earthquakes and the 2011 Mw9.0 Tohoku-oki earthquake.Our results show:(1)Changbaishan has experienced four stages of unrest since 1999,and the biggest unrest of the shallow magma chamber occurred from 2002 to 2005;(2)the parameters of the shallow magma chamber simulated by the Mogi and Point Compound Dislocation Model(p DCM)show that the magma chamber is located in the northern part of the crater,with a depth of approximately 7 km.The volume of the magma chamber increased by 25-28×10^(6) m from 2002 to2005;(3)the strain variation beneath the Changbaishan volcano corresponding to the 1999 Wangqing earthquake was small.The 2002 Wangqing earthquake produced an expansion strain of about 4.4 nanostrain on the magma chamber at a depth of 550 km,and probably promoted the unrest of the Changbaishan volcano.The 2011 Tohoku earthquake induced the expansion of the shallow magma chamber and compression of the deep magma chamber.Although this event promoted shallow magma unrest,it inhibited deep magma unrest.This may explain why the Changbaishan did not show obvious unrest after the 2011 Tohoku earthquake.Therefore,more attention should be paid to earthquakes that can promote deep magma unrest in the Changbaishan volcano.

Thermodynamic prediction of martensitic transformation temperature in Fe-C-X(X=Ni,Mn,Si,Cr)systems with dilatational coefficient model

Martensitic transformation is significant to strengthen steels,but its thermodynamic prediction is restricted to simple systems due to lacking multicomponent interaction parameters.The driving forces of martensitic transformation can be divided into chemical and non-chemical driving forces.The magnetic parameters are carefully optimized because it affects the magnetic Gibbs free energy of austenite and ferrite,and have big impact on the chemical driving force.The dilatational strain energy provides major contribution to non-chemical driving force,thus the integrated-models for dilatational coefficient are constructed in a wide composition and temperature range based on the experimental dilatational data.It expands the scope of application of thermodynamic model and improved prediction accuracy of martensitic transformation temperature(M_(s)).The prediction error reaches 5.6%for Fe-C-X(X=Ni,Mn,Si,Cr)and6.5%for Fe-C-Mn-Si-X(X=Cr,Ni)steels.