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The 1989 Mw 6.9 Loma Prieta earthquake is the first major event to occur along the San Andreas fault (SAF) zone in central California since the 1906 M 7.9 San Francisco earthquake. Given the complexity of this event, uncertainty has persisted as to whether this earthquake ruptured the SAF itself or a secondary fault. Recent work on the SAF in the Coachella Valley in southern California has revealed similar complexity, arising from a nonplanar, nonvertical fault geometry, and has led us to reexamine the Loma Prieta event. We have compiled data sets and data analyses in the vicinity of the Loma Prieta earthquake, including the 3D seismic velocity model and aftershock relocations of Lin and Thurber (2012), potential field data collected by the U.S. Geological Survey following the earthquake, and seismic refraction and reflection data from the 1991 profile of Catchings et al. (2004). The velocity model and aftershock relocations of Lin and Thurber (2012) reveal a geometry for the SAF that appears similar to that in the Coachella Valley (although rotated 180°): at Loma Prieta the fault dips steeply near the surface and curves with depth to join the moderately southwest-dipping main rupture below 6 km depth, itself also nonplanar. The SAF is a clear velocity boundary, with higher velocities on the northeast, attributable to Mesozoic accretionary and other rocks, and lower velocities on the southwest, attributable to Cenozoic sedimentary and volcanic rocks of the La Honda block. Rocks of the La Honda block have been offset right-laterally hundreds of kilometers from similar rocks in the southern San Joaquin Valley and vicinity, providing evidence that the curved northeast fault boundary of this block is the plate boundary. Thus, we interpret that the Loma Prieta earthquake occurred on the SAF and not on a secondary fault. [ABSTRACT FROM AUTHOR]

I present a frequency-independent 3D seismic attenuation model (indicated by QP-1 ) for the crust of the Salton trough and the adjacent regions in southeastern southern California. The simul2000 tomographic algorithm was used to invert the frequency-independent attenuation operator t* values measured from amplitude spectra of 23,378 P-wave arrivals of 1203 events through a recently developed 3D velocity model. The QP model has a uniform horizontal grid spacing of 5 km, and the vertical-node intervals range between 2 and 5 km down to 27 km depth. In general, the QP values increase with depth and agree with the surface geology in the shallow depth layers. Low QP values are observed in the Imperial Valley, California, which are consistent with the sedimentary deposits and may also reflect the presence of pore fluid in the active fault zones, whereas greatly elevated QP values are shown in the surrounding crystalline ranges. The new QP model provides an important complement to the existing velocity models for interpreting structural heterogeneity and fluid saturation of rocks in the study area. [ABSTRACT FROM AUTHOR]

I present a new 3D seismic velocity model and high-precision earthquake relocations between 1981 and 2010 near the Saltón Trough and the San Jacinto fault zone. The simul 2000 tomography algorithm is applied to derive the 3D VP and VP/VS models using first arrivals of a composite event data set. The final VP model correlates with geological features at shallow depths and is more consistent with the refraction studies than the starting 3D regional-scale model. The VP/VS model shows strong variations in the upper crust and is dominated by relatively low values (below 1.7) in the middle crust except for the Salton Trough and the Imperial Valley. The newly resolved model is used to relocate all the seismicity in the study area. I then apply the similar-event cluster analysis and differential-time relocation approach based on waveform cross-correlation data to the 3D relocated events. A dramatic sharpening of seismicity patterns is obtained after using these methods. The new locations are more tightly clustered than the previous catalogs mainly due to the different absolute locations. The depth distribution along a basal surface may suggest the existence of a detachment fault from the north end of the Salton Trough to United States-Mexico border. The fine-scale velocity structure and precise earthquake relocations will be helpful for investigating the fault geometry, seismicity, stress interaction, and other seismological studies for southern California. [ABSTRACT FROM AUTHOR]

Abstract: Yinfu Reservoir is an important source of water supply of Qingdao. The field investigation was conducted on this reservoir in the summer of 2010. Five sampling points were placed on the tributaries around the reservoir. Severn sampling sites in 3 layers (surface, middle layer, bottom) to take water samples were arranged. Monitoring objects include: T, pH, SD, TP, TN, Chl-a, salinity, TDS, conductivity. The spatial variations of water quality were analyzed. The results showed that the salinity, conductivity, TDS, TN concentrations of reservoir monitoring points around the tributaries were generally higher compared to the inner monitoring sites. The concentration of TN reached the Four water standards; little difference existed in the concentration of TP and DO, up to A water standard; the content of Chl-a in the outer monitoring points is lower than that of the inner. The content of total nitrogen in the surface and bottom of the reservoir was higher. The content of Chl-a is highest in the surface of reservoir; the content of suspended matter increased with water depths, however, no significant changes in conductivity and salinity with depth. The analysis of water quality data of years showed that the content of nitrogen in the reservoir is closely linked with rainfall. The content of total nitrogen in the dry season is always highest while the content of COD in the wet season is highest. [Copyright &y& Elsevier]

Abstract: The protection and utilization of wetland have been more and more important. According to measured water levels, discharge and cross-sections of the Shuangtaizi River network, this paper builds a hydrodynamic model to simulate water and salt movement based on the Mike11. The model was calibrated and validated by measured water levels of July, 2009. A series of irrigation scheme for the reed field were designed according to the hydrological characteristics of the wetland. The results show that volume of water shortage is 65.1 million cubic meters in dry years, 4.2 million cubic meters in average years and 40.5 million cubic meters in wet years. With the expansion of water facilities, the water shortage reduced to 30.6 million cubic meters, 16.3 million cubic meters and 17.4 million cubic meters respectively in dry years, average years and wet years. In wet years and average years, salinity of tidal prism water can satisfy the requirements of irrigation. However, due to high tide salinity in dry years, irrigation can not be directly used for the reed field. [Copyright &y& Elsevier]

We obtain a seismic velocity model of the California crust and uppermost mantle using a regional-scale double-difference tomography algorithm. We begin by using absolute arrival-time picks to solve for a coarse three-dimensional (3D) P velocity (VP) model with a uniform 30 km horizontal node spacing, which we then use as the starting model for a finer-scale inversion using double-difference tomography applied to absolute and differential pick times. For computational reasons, we split the state into 5 subregions with a grid spacing of 10 to 20 km and assemble our final statewide VP model by stitching together these local models. We also solve for a statewide S-wave model using S picks from both the Southern California Seismic Network and USArray, assuming a starting model based on the VP results and a VP/VS ratio of 1.732. Our new model has improved areal coverage compared with previous models, extending 570 km in the SW-NE direction and 1320 km in the NW-SE direction. It also extends to greater depth due to the inclusion of substantial data at large epicentral distances. Our VP model generally agrees with previous separate regional models for northern and southern California, but we also observe some new features, such as high-velocity anomalies at shallow depths in the Klamath Mountains and Mount Shasta area, somewhat slow velocities in the northern Coast Ranges, and slow anomalies beneath the Sierra Nevada at midcrustal and greater depths. This model can be applied to a variety of regional-scale studies in California, such as developing a unified statewide earthquake location catalog and performing regional waveform modeling. [ABSTRACT FROM AUTHOR]

We use relative arrival times and locations for similar earthquake pairs that are found using a cross-correlation method to analyze the time dependence of P and S station terms in southern California from 1984 to 2002.We examine 494 similar event clusters recorded by Southern California Seismic Network (SCSN) stations and compute absolute arrival-time variations from the differential arrival-time residuals obtained following event relocation. We compute station terms from the robust means of the absolute arrival-time residuals from all events recorded by each station at 3-month intervals. We observe nine stations with abrupt offsets in timing of 20-70 msec, which are likely caused by equipment changes during our study period. Taking these changes into account could improve the relative location accuracy for some of the event clusters. For other stations, we generally do not see systematic temporal variations greater than about 10 msec. Analysis of residuals along individual ray paths does not reveal any clear localized regions of apparent velocity changes at depth. These results limit large-scale, long-lasting temporal variations in P and S velocities across southern California during this time period to less than about ±0:2%. However, there is an increased fraction of individual travel-time residuals exceeding 20 msec immediately following major earthquakes from source regions near the mainshock rupture. [ABSTRACT FROM AUTHOR]

We develop and test a method to estimate local Vp/Vs ratios for compact similar earthquake clusters using the precise P and S differential times obtained using waveform cross-correlation. We demonstrate how our technique works using synthetic data and evaluate likely errors arising from near-source takeoff angle differences between P and S waves. We use a robust misfit function method to compute Vp/Vs ratios for both synthetic data sets and several similar event clusters in southern California, and use a bootstrap resampling approach to estimate standard errors for real data. Our technique has higher resolution for near-source Vp/Vs ratios than typical tomographic inversion methods and provides constraints on near-fault rock properties. [ABSTRACT FROM AUTHOR]

We obtain absolute locations for 19 clusters of mining-induced seismicity in southern California by identifying quarries using remote sensing data, including optical imagery and differential digital elevation models. These seismicity clusters contain 16,574 events from the Southern California Seismic Network from 1984 to 2002, which are flagged as quarry blasts but without any ground-truth location constraints. Using georeferenced airphotos and satellite radar topography data, we identify the likely sources of these events as quarries that are clearly visible within 1 to 2 km of the seismically determined locations. We then shift the clusters to align with the airphoto images, obtaining an estimated absolute location accuracy of ∼200 m for the cluster centroids. The improved locations of these explosions should be helpful for constraining regional 3D velocity models. [ABSTRACT FROM AUTHOR]

We obtain precise relative relocations for more than 340,000 southern California earthquakes between 1984 and 2002 by applying the source-specific station-term (SSST) method to existing P- and S-phase picks and a differential location method to about 208,000 events within similar-event clusters identified with waveform cross-correlation. The entire catalog is first relocated by using existing phase picks, a reference 1D velocity model, and the SSST method of Richards-Dinger and Shearer (2000). We also perform separate relocations of Imperial Valley events by using a velocity model more suited to this region. Next, we apply cluster analysis to the waveform cross-correlation output to identify similar-event clusters. We relocate earthquakes within each similar-event cluster by using the differential times alone, keeping the cluster centroid fixed to its initial SSST location. We estimate standard errors for the relative locations from the internal consistency of differential locations between individual event pairs; these errors are often as small as tens of meters. In many cases the relocated events within each similar-event cluster align in planar features suggestive of faults. We observe a surprising number of such faults at small scales that strike nearly perpendicular to the main seismicity trends. In general, the fine-scale details of the seismicity reveal a great deal of structural complexity in southern California fault systems. [ABSTRACT FROM AUTHOR]