Spheroidal oscillations of the Earth stimulated by the Sumatra-Andaman earthquake with CDSN data

The 0S2-0S54 spheroidal modes of Earth＇s free oscillations, triggered by the great Sumatra-Andaman earthquake of 26 December 2004 are retrieved from VHZ data recorded by seven upgraded stations of China Digital Seismograph Network （CDSN）. We compare these spheroidal modes with theoretical free oscillation spectra calculated from the Preliminary Reference Earth Model （PREM） and find a coincidence between their periods. Spectral splitting phenomenon is observed obviously in 0S2, 0S3, 0S4, 2S1 and 1S2 free oscillation modes. What is most noticeable is that the oscillation mode 2S1 is reported for the second time （the first time by Rosat et al） without any data stacking. We simulated the split singlet of 0S2 mode on seven CDSN stations based on general focal mechanism and seismic moment of the earthquake. The result shows that seismic moment of the earthquake can reach 10^23 N.m. We also find that the recording of Earth＇s free oscillations carries abundant information of source mechanism and earthquake location, which is applicable to the detailed study of source rupture parameters.

Studying of Deformation Processes by Two-Coordinate Laser Strainmeter

The results of experimental data processing of a two-coordinate laser strainmeter are discussed. The two-coordinate laser strainmeter consists of two laser strainmeters which measuring shoulders are oriented along the lines “North- South” and “West-East”. Measurement accuracy of the earth's crust microdisplacements of these devices makes 0 to1 nm. Working frequency range is from 0 to 1000 Hz. Processing experimental data the main attention is paid to high tides, natural oscillations of the Earth, natural oscillations of geoblocks, superficial sea waves. It is established that after separate earthquakes the natural oscillations of regional geoblocks are strongly excited. Besides, it is revealed that quasiperiodic fluctuations of crust in the range of periods from 1 to 12 min. are caused by atmospheric processes. Besides, it is revealed that quasiperiodic oscillations of the earth's crust in the range of periods from 1 to 12 minutes are caused by atmospheric processes.

Climatology of the Meteorological Factors Associated with Haze Events over Northern China and Their Potential Response to the Quasi-Biannual Oscillation

An upswing in haze weather during autumn and winter has been observed over North and Northeast China in re- cent years, imposing adverse impacts upon local socioeconomic development and human health. However, such an increase in the occurrence of haze events and its association with natural climate variability and climate change are not well understood. To investigate the climatology of the meteorological factors associated with haze events and their natural variability, this study uses a meteorological pollution index called PLAM （Parameter Linking Air-qual- ity to Meteorological conditions） and ERA-Interim reanalysis data. The results suggest that high PLAM values tend to occur over southern parts of northem China, implying the weather conditions over this area are favorable for the occurrence of haze weather. For the period 1979-2014, the regional mean PLAM shows an overall increase across Beijing, Tianjin, and Hebei Province, and parts of Shanxi Province. Also, a periodicity of 28-34 months is found in the temporal variation of PLAM, which implies a potential association of PLAM with the stratospheric Quasi-Bian- nual Oscillation （QBO）. By using the QBO index during the autumn and winter seasons in the preceding year, an in- crease in PLAM is found for the westerly phases of the QBO, relative to the easterly phases. An upper-tropospheric warming is also found in the westerly phases, which can induce a stable stratification that favors the increase in PLAM across the midlatitudes. The modulations of large-scale environmental factors, including moist static stability, vertical velocity, and temperattu＇e advection, also act to enhance PLAM in the westerly phases. However, the baro- clinic term of moist potential vorticity at 700 hPa tends to decrease over the south, and an increase in low-level as- cent is found over the north. These factors can reduce PLAM and possibly limit the statistical significance of the in- creased PLAM in the westerly phases of the QBO.