ALBERT

Description: The M w  7.0 Kumamoto, Japan, earthquake occurred on 15 April 2016 at 16:25 UTC. Using ground accelerations recorded by 104 near-field stations, we investigate spatial variability of observed ground motions, apparent period dependence, and azimuthal variation, as well as rupture directivity effects on various intensity measures. We develop a simplified ground-motion model that includes both geometric and anelastic attenuation terms. Comparisons of observed and predicted ground motions suggest that predictions from the Next Generation Attenuation-West2 models provide good fits for the overall observation. Analysis of spatial distribution of the residuals shows that observed peak ground velocity (PGV) and long-period spectral accelerations (SAs) in the 150°–180° azimuth range along the rupture backward direction (southwest of the fault) can be as low as 0.3–0.8 times the average observation of this event. Long-period ground motions on the northeast side of the fault in the forward direction are much higher than average, with PGV and long-period SAs ranging from 1.2 to 1.5 times the average. There is clear period dependence of the strong ground motion variation. The biases due to directivity generally decrease with decreasing period for all azimuth ranges. On the distance dependence of directivity effects, our study shows that directivity effects can be considered practically nonsignificant for stations close to the hypocenter. We also perform a log–linear regression of the residuals, using a new directivity predictor. Our results show that for the 2016 M w  7.0 Kumamoto earthquake, rupture directivity produces significant amplifications in the rupture forward direction, whereas deamplification effects are observed in the rupture backward region. Directivity effects are particularly relevant for PGV and long-period SA (i.e., SA at periods ≥2.0 s). Such effects do not have systematic influence on peak ground acceleration and short-period ground motions (i.e., SA at periods 〈2.0 s). Electronic Supplement: Figures of variation of regression residuals with R rup for observed peak ground acceleration (PGA), peak ground velocity (PGV), and spectral accelerations (SAs) and of regression residuals versus V S 30 .

Description: Earthquake ground-motion prediction models usually define site conditions based on the time-averaged shear-wave velocity in the upper 30 m ( V S 30 ). Proxy-based estimations of V S 30 are commonly used, if velocity measurements are not available. We compile a soil-profile database for the Beijing plain area (China), using data from research documents and technical reports. The database contains 479 soil profiles, 463 of which have depths greater than 30 m. We develop regional relationships for the Beijing plain area for extrapolating the time-averaged shear-wave velocity to a given depth less than 30 m to V S 30 , and then compare the performance of available models. We find that the second-order polynomial model ( Boore et al. , 2011 ), based on data from Japan, provides an overprediction, whereas the linear model ( Boore, 2004 ) calibrated on data from California underestimates V S 30 . We develop relationships for estimating V S 30 based on proxies such as ground slope gradients from radar-derived digital elevation models (DEMs) and surface geology at different scales. We find that local V S 30 data in the Beijing plain are generally lower than existing 30 arcsec gradient-based global models. Regression results show a modest correlation between V S 30 and topographic ground slope for several DEM resolutions (3, 15, 30, and 60 arcsec). Geology-based proxies are more effective than ground slope for V S 30 estimation in the analyzed area. We propose a bilinear model based on geologic ages and depositional environments for estimating V S 30 , which shows a statistically significant trend for application in the Beijing plain area. Online Material: Figures showing topographic ground slopes and correlations of V S 30 with topographic slope from digital elevation model (DEM) data and a table summarizing data from the 463 boreholes.

Description: Using the curved grid finite-difference method, we develop dynamic spontaneous rupture models of earthquakes on the Jiaocheng fault (JF) near Taiyuan, the capital and largest city of Shanxi Province in north China. We then model the wave propagation and strong ground motion generated by these scenario earthquakes. A map of the seismic-hazard distribution for a potential M  7.5 earthquake is created based on dynamic rupture and true 3D modeling. The tectonic initial stress fields derived from the inversion of focal mechanisms of historical earthquakes, a nonplanar fault, and a rough surface are considered in the dynamic rupture simulation. Based on the geological structure of the Taiyuan basin, normal faulting with a dipping angle of 60° is implemented for the scenario earthquake simulations. The largest uncertainty of a potential earthquake in the JF zone is the hypocenter. Four cases are used to nucleate the earthquake at different locations. Using these dynamic rupture sources for the JF, we further simulate and analyze both the seismic wave generated by the scenario earthquake and the strong ground motion. It is found that the low-velocity media of the Taiyuan basin redistribute the ground motion well. The effects of the regional stress fields on the dynamic rupture and hazard distribution are investigated and discussed further. Moreover, a scenario earthquake, which can cause great damage to the city of Taiyuan, is modeled and analyzed.

Description: The legacy of long-term mining activities in Wanshan mercury (Hg) mining area (WMMA), Guizhou, China including a series of environmental issues related to Hg pollution. The spatial distribution of gaseous elemental mercury (Hg0) concentrations in ambient air were monitored using a mobile RA-915+ Zeeman Mercury Analyzer during daytime and night time in May 2010. The data imply that calcines and mine wastes piles located at Dashuixi and on-going artisanal Hg mining activities at Supeng were major sources of atmospheric mercury in WMMA. For a full year (May 2010 to May 2011), sampling of precipitation and throughfall were conducted on a weekly basis at three sites (Shenchong, Dashuixi, and Supeng) within WMMA. Hg in deposition was characterized by analysis of total Hg (THg) and dissolved Hg (DHg) concentrations. The corresponding data exhibit a high degree of variability, both temporarily and spatially. The volume-weighted mean THg concentrations in precipitation and throughfall samples were 502.6 ng l−1 and 977.8 ng l−1 at Shenchong, 814.1 ng l−1and 3392.1 ng l−1 at Dashuixi, 7490.1 ng l−1and 9641.5 ng l−1 at Supeng, respectively. THg was enhanced in throughfall compared to wet deposition samples by up to a factor of 7. The annual wet Hg deposition fluxes were 29.1, 68.8 and 593.1 μg m−2 yr−1 at Shenchong, Dashuixi and Supeng, respectively, while the annual dry Hg deposition fluxes were estimated to be 378.9, 2613.6 and 6178 μg m−2 yr−1 at these sites, respectively. Dry deposition played a dominant role in total atmospheric Hg deposition in WMMA since the dry deposition fluxes were 10.4–37.9 times higher than the wet deposition fluxes during the whole sample period. Our data showed that air deposition was still an important pathway of Hg contamination to the local environment in WMMA.

Description: The aerosol extinction-to-backscatter ratio is an important parameter for inverting LIDAR signals in the LIDAR equation. It is a complicated function of the aerosol microphysical characteristics. In this paper, a method to retrieve the column-averaged aerosol extinction-to-backscatter ratio by constraining the aerosol optical depths (AOD) from a Micro-pulse LIDAR (MPL) by the AOD measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) is presented. Both measurements were taken on cloud free days between 1 May 2003 and 30 June 2004 over Hong Kong, a coastal city in south China. Simultaneous measurements of aerosol scattering coefficients with a forward scattering visibility sensor are compared with the LIDAR retrieval of aerosol extinction coefficients. The data are then analyzed to determine seasonal trends of the aetrosol extinction-to-backscatter ratio. In addition, the relationships between the extinction-to-backscatter ratio and wind conditions as well as other aerosol microphysical parameters are presented. The mean aerosol extinction-to-backscatter ratio for the whole period was found to be 29.1±5.8 sr, with a minimum of 18 sr in July 2003 and a maximum of 44 sr in March 2004. The ratio is lower in summer because of the dominance of oceanic aerosols in association with the prevailing southwesterly monsoon. In contrast, relatively larger ratios are noted in spring and winter because of the increased impact of local and regional industrial pollutants associated with the northerly monsoon. The extended LIDAR measurements over Hong Kong provide not only a more accurate retrieval of aerosol extinction coefficient profiles, but also significant substantial information for air pollution and climate studies in the region.

Description: China disposes of bulk Municipal Solid Waste (MSW) by landfilling, resulting in a large quantity of mercury that enters landfills through waste. A detailed study on atmospheric mercury emissions from MSW landfills in China is necessary to understand mercury behavior from this source. Between 2003 and 2006, mercury airborne emissions through different pathways, as well as mercury speciation in Landfill Gas (LFG) were measured at 5 MSW landfills in Guiyang and Wuhan, China. The results showed that mercury content in the substrate increased the magnitude of mercury emissions, with the highest emission rate measured at the working face and in uncovered waste areas, and the lowest measured near soil covers and vegetated areas. Meteorological parameters, especially solar radiation, influenced the diurnal pattern of mercury surface-air emissions. Total Gaseous Mercury (TGM) in LFG varied from 2.0 to 1406.0 ng m−3, Monomethyl Mercury (MMHg) and Dimethyl Mercury (DMHg) in LFG averaged at 1.93 and 9.21 ng m−3, and accounted for 0.51% and 1.79% of the TGM in the LFG, respectively. Total mercury emitted from the five landfills ranged from 17 to 3300 g yr−1, with the highest from the working face, then soil covering, and finally the vent pipes.

Description: Atmospheric hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) were measured in-situ at the Shangdianzi (SDZ) Global Atmosphere Watch (GAW) regional background station, China, from May 2010 to May 2011. The time series for five HFCs and three PFCs showed occasionally high-concentration events while background conditions occurred for 36% (HFC-32) to 83% (PFC-218) of all measurements. The mean mixing ratios during background conditions were 24.5 ppt (parts per trillion, 10−12, molar) for HFC-23, 5.86 ppt for HFC-32, 9.97 ppt for HFC-125, 66.0 ppt for HFC-134a, 9.77 ppt for HFC-152a, 79.1 ppt for CF4, 4.22 ppt for PFC-116, and 0.56 ppt for PFC-218. The background mixing ratios for the compounds at SDZ are consistent with those obtained at mid to high latitude sites in the Northern Hemisphere. North-easterly winds were associated with negative contributions to atmospheric HFC and PFC loadings (mixing ratio anomalies weighted by time associated with winds in a given sector), whereas south-westerly advection (urban sector) showed positive loadings. Chinese emissions estimated by a tracer ratio method using carbon monoxide as tracer were 3.6 ± 3.2 kt yr−1 for HFC-23, 4.3 ± 3.6 kt yr−1 for HFC-32, 2.7 ± 2.3 kt yr−1 for HFC-125, 6.0 ± 5.6 kt yr−1 for HFC-134a, 2.0 ± 1.8 kt yr−1 for HFC-152a, 2.4 ± 2.1 kt yr−1 for CF4, 0.27 ± 0.26 kt yr−1 for PFC-116, and 0.061 ± 0.095 kt yr−1 for PFC-218. The lower HFC-23 emissions compared to earlier studies may be a result of the HFC-23 abatement measures taken as part of Clean Development Mechanism (CDM) projects that started in 2005.

Description: In-situ measurements of atmospheric hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) have been conducted at the Shangdianzi (SDZ) Global Atmosphere Watch (GAW) regional background station, China, from May 2010 to May 2011. The time series for 5 HFCs and 4 PFCs periodically showed high concentration events while background conditions occurred for 36% (HFC-32) to 83% (PFC-218) of all measurements. The mean mixing ratios during background conditions for HFC-23, HFC-32, HFC-125, HFC-134a, HFC-152, CF4, PFC-116, PFC-218 and PFC-318 were 24.5, 5.86, 9.97, 66.0, 9.77, 79.1, 4.22, 0.56, 1.28 ppt (parts per trillion, 10−12, molar), respectively. The background mixing ratios for the compounds at SDZ are consistent with those obtained at mid to high latitude sites in the Northern Hemisphere, except for HFC-32 and PFC-318 for which background mixing ratios were not reported in recent years. All HFCs and PFCs show positive trends at rates of 0.7, 1.4, 1.6, 4.1, 1.1, 0.43, 0.05, 0.01, 0.04 ppt yr−1 for HFC-23, HFC-32, HFC-125, HFC-134a, HFC-152, CF4, PFC-116, PFC-218 and PFC-318, respectively. North-easterly winds were connected with small contributions to atmospheric HFCs and PFCs loadings, whereas south-westerly advection (urban sector) showed increased loadings. Chinese emissions were estimated by a tracer ratio method using CO as tracer with rather well known emissions. The emissions, as derived from our measurement period, were 4.4 ± 0.7, 6.9 ± 0.9, 2.5 ± 0.3, 9.0 ± 1.3, 2.2 ± 0.4, 2.1 ± 0.3, 0.24 ± 0.06, 0.07 ± 0.04, 0.45 ± 0.09 kt yr−1 for HFC-23, HFC-32, HFC-125, HFC-134a, HFC-152, CF4, PFC-116, PFC-218, and PFC-318, respectively. The lower HFC-23 emissions compared to earlier studies may be a result of the HFC-23 abatement measures taken as part of the Clean Development Mechanism (CDM) project that started in 2005.

Description: Forests play a leading role in regional and global terrestrial carbon (C) cycles. Changes in C sequestration within forests can be attributed to areal expansion (increase in forest area) and forest growth (increase in biomass density). Detailed assessment of the relative contributions of areal expansion and forest growth to C sinks is crucial to reveal the mechanisms that control forest C sinks and is helpful for developing sustainable forest management policies in the face of climate change. Using the Forest Identity concept and forest inventory data, this study quantified the spatial and temporal changes in the relative contributions of forest areal expansion and increased biomass growth to China's forest C sinks from 1977 to 2008. Over the last 30 years, the areal expansion of forests was a larger contributor to C sinks than forest growth for all forests and planted forests in China (74.6 vs. 25.4 % for all forests, and 62.4 vs. 37.8 % for plantations). However, for natural forests, forest growth made a larger contribution than areal expansion (60.4 vs. 39.6 %). The relative contribution of forest growth of planted forests showed an increasing trend from an initial 25.3 to 61.0 % in the later period of 1998 to 2003, but for natural forests, the relative contributions were variable without clear trends owing to the drastic changes in forest area and biomass density over the last 30 years. Our findings suggest that afforestation can continue to increase the C sink of China's forests in the future subject to persistently-increasing forest growth after establishment of plantation.

Description: Accurate and reliable drought monitoring is of primary importance for drought mitigation and reduction of social-ecological vulnerability. The aim of the paper was to propose a short-term/long-term composited drought index (CDI) which could be widely used for drought monitoring and early warning in China. In the study, the upper Huaihe River basin above the Xixian gauge station, which has been hit by severe droughts frequently in recent decades, was selected as the case study site. The short-term CDI was developed by the Principle Component Analysis of the self-calibrating Palmer Drought Severity Index (sc-PDSI), the 1- and 3-month Standardized Precipitation Evapotranspiration Index (SPEI), Z Index (ZIND), the Soil Moisture Index (SMI) with the long-term CDI being formulated by use of the self-calibrating Palmer Hydrology Drought Index (sc-PHDI), the 6-, 12-, 18- and 24-month SPEI, the Standardized Streamflow Index (SSI), the SMI. The sc-PDSI, the PHDI, the ZIND, the SPEI on a monthly time scale were calculated based on the monthly air temperature and precipitation, and the monthly SMI and SSI were computed based on the simulated soil moisture and runoff by the distributed Xinanjiang model. The thresholds of the short-term/long-term CDI were determined according to frequency statistics of different drought indices. Finally, the feasibility of the two CDIs was investigated against the scPDSI, the SPEI and the historical drought records. The results revealed that the short-term/long-term CDI could capture the onset, severity, persistence of drought events very well with the former being better at identifying the dynamic evolution of drought condition while the latter better at judging the changing trend of drought over a long time period.