Seismology Characteristics Of The North Korean’s Nuclear Explosions And Three-dimension Attenuation Structure Of Upper Mantle Under The Changbai Volcano

The North Korea’s nuclear test has always been the focus of internationalattention for a long time. Denuclearization of the Korean peninsula has become theearnest expectation of people around the world. With further accelerate the pace ofNorth Korea’s nuclear test, it conducted two nuclear tests in2009and2013followingthe2006nuclear test, and the scale of it is increasing. This makes the North Korean’snuclear test have also attracted wide attention in the scientific community. How toquickly and accurately locate the positon of nuclear test, estimate yield and assess ofits cause radiological hazard became the focus of attention of scientists.In this paper, we make a research of seismology characteristics and attenuationof the two North Korean nuclear tests in2009and2013by using two North Koreannuclear waveform data recorded by temporary seismic stations located in ChangbaiMountain region. In order to compare with the nuclear explosion, we selected twonatural earthquakes to recognize nuclear explosion by comparing characteristics ofnuclear explosion and earthquake signals in the time-frequency domain. We selecteddifferent phases based on group velocity windows and compared seismologycharacteristic of the different phases, and then make a further and more reasonableexplanation from the perspective of the focal mechanism. P/S-style spectral ratios is aeffective method to discriminate nuclear explosion. We discriminate successfullybetween two North Korean nuclear tests at frequency above2Hz. By comparing thetwo nuclear explosion spectral ratio curve. We make a conclusion that nuclearenergy in2013is larger than its in2009combined with the previous research.In addition, the temporary stations that recorded two nuclear explosion located inthe west of Changbai Mountain and Liaoning province, nuclear explosion signaltravel under the Changbai volcano and the crust of the North China have strongattenuation because of low velocity and high conductivity in this area. Since theattenuation factor is an important parameter of inelastic attenuation and inverse Qmodel. We selected two nuclear explosion signal recorded by temporary stations tocalculate attenuation factor, combined with P wave velocity model obtained simpleattenuation structure in Changbai Moutain area. It also provide initial Q model fortree-dimension attenuation tomography.The Changbai volcano is an active volcano that have potential danger of eruption.Research of telluric electromagnetic sounding and seismic tomography show that there is low velocity and high conductivity area in crust and upper mantle under theChangbai volcano. And depth of it is about400km, a width of it is about200km. Inorder to make a further research about the Changbai volcano, such as distribution ofthe magma chamber in the mantle, the origin of the Changbai volcano and so on. weinvestigate tree-dimension attenuation structure of upper mantle under the Changbaivolcano by using85teleseismic event that is selected by conditions that epicentraldistance between30o~85o and focal depth greater than200km from2009to2013.Obtain three-dimension attenuation model in the first time. Our results suggest thatthere is a depth of400km range high attenuation area under the Changbai volcanoand combined with velocity model and evidence of petrology, geothermic, electricalconductivity, we make a conclusion that the origin of the Changbai volcano is relatedto the deep dehydration of the stagnant Pacific slab in the mantle transition zone.