Will Chang | University of California, Berkeley (original) (raw)

Papers by Will Chang

Research paper thumbnail of Temperature Evolution in a Shallow Aquifer Above a Steamed Heavy-Oil Reservoir in the San Ardo Oil Field, Monterey County, California

Research paper thumbnail of Exploring Phonological Areality in the Circum-Andean Region Using a Naive Bayes Classifier

Quantifying Language Dynamics, 2014

This paper describes the Core and Periphery technique, a quantitative method for exploring areali... more This paper describes the Core and Periphery technique, a quantitative method for exploring areality that uses a naive Bayes classifier, a statistical tool for inferring class membership based on training sets assembled from members of those classes. The Core and Periphery technique is applied to the exploration of phonological areality in the Andes and surrounding lowland regions, based on the South American Phonological Inventory database (SAPhon 1.1.3; Michael, Stark, and Chang 2013). Evidence is found for a phonological area centering on the Andean highlands, and extending to parts of the northern and central Andean foothills regions, the Chaco, and Patagonia. Evidence is also found for Southern and North-Central phonological sub-areas within this larger phonological area.

Research paper thumbnail of Exploring Phonological Areality in the Circum-Andean Region Using a Naive Bayes Classifier

Quantifying Language Dynamics, 2014

This paper describes the Core and Periphery technique, a quantitative method for exploring areali... more This paper describes the Core and Periphery technique, a quantitative method for exploring areality that uses a naive Bayes classifier, a statistical tool for inferring class membership based on training sets assembled from members of those classes. The Core and Periphery technique is applied to the exploration of phonological areality in the Andes and surrounding lowland regions, based on the South American Phonological Inventory database (SAPhon 1.1.3; Michael, Stark, and Chang 2013). Evidence is found for a phonological area centering on the Andean highlands, and extending to parts of the northern and central Andean foothills regions, the Chaco, and Patagonia. Evidence is also found for Southern and North-Central phonological sub-areas within this larger phonological area.

Research paper thumbnail of Mapping aquifer salinity gradients and effects of oil field produced water disposal using geophysical logs: Elk Hills, Buena Vista and Coles Levee Oil Fields, San Joaquin Valley, California

PLOS ONE

The effects of oil and gas production on adjacent groundwater quality are becoming a concern in m... more The effects of oil and gas production on adjacent groundwater quality are becoming a concern in many areas of the United States. As a result, it has become increasingly important to identify which aquifers require monitoring and protection. In this study, we map the extent of groundwater with less than 10,000 mg/L TDS both laterally and vertically near the Elk Hills, Buena Vista and Coles Levee Oil Fields in the San Joaquin Valley, California and note evidence of effects of produced water disposal on salinity within the Tulare aquifer. Subsurface maps showing the depth at which groundwater salinity is less than 10,000 mg/L (or Base 10K) in the Tulare aquifer are generated using geophysical logs and verified by comparison to water sample analyses. The depth to Base 10K ranges from 240 m (800 ft) in Elk Hills to 800 m (2650 ft) in the adjacent Buena Vista syncline and is 670 m (2,200 ft) deep in the Coles Levee area to the east. Log-calculated salinities show a relatively smooth incre...

Research paper thumbnail of Correction: Stratigraphic and structural controls on groundwater salinity variations in the Poso Creek Oil Field, Kern County, California, USA

Hydrogeology Journal

Figure S4 in the electronic supplementary material (ESM) has been replaced to display the correct... more Figure S4 in the electronic supplementary material (ESM) has been replaced to display the correct contours. The original article has been corrected.

Research paper thumbnail of Stratigraphic and structural controls on groundwater salinity variations in the Poso Creek Oil Field, Kern County, California, USA

Hydrogeology Journal

Groundwater total dissolved solids (TDS) distribution was mapped with a three-dimensional (3D) mo... more Groundwater total dissolved solids (TDS) distribution was mapped with a three-dimensional (3D) model, and it was found that TDS variability is largely controlled by stratigraphy and geologic structure. General TDS patterns in the San Joaquin Valley of California (USA) are attributed to predominantly connate water composition and large-scale recharge from the adjacent Sierra Nevada. However, in smaller areas, stratigraphy and faulting play an important role in controlling TDS. Here, the relationship of stratigraphy and structure to TDS concentration was examined at Poso Creek Oil Field, Kern County, California. The TDS model was constructed using produced water TDS samples and borehole geophysics. The model was used to predict TDS concentration at discrete locations in 3D space and used a Gaussian process to interpolate TDS over a volume. In the overlying aquifer, TDS is typically <1,000 mg/L and increases with depth to ~1,200–3,500 mg/L in the hydrocarbon zone below the Macoma cl...

Research paper thumbnail of Groundwater salinity mapping using geophysical log analysis within the Fruitvale and Rosedale Ranch oil fields, Kern County, California, USA

Hydrogeology Journal

A method is presented for deriving a volume model of groundwater total dissolved solids (TDS) fro... more A method is presented for deriving a volume model of groundwater total dissolved solids (TDS) from borehole geophysical and aqueous geochemical measurements. While previous TDS mapping techniques have proved useful in the hydrogeologic setting in which they were developed, they may yield poor results in settings with lithological heterogeneity, complex water chemistry, or limited data. Problems arise because of assumed values for empirical constants in Archie's Equation, unrealistic porosity and temperature gradients, or bicarbonate-rich groundwater. These issues become critical in complex geologic settings such as the San Joaquin Valley of California, USA. To address this, a method to map TDS in three dimensions is applied to the Fruitvale and Rosedale Ranch oil fields near Bakersfield, California. Borehole resistivity, porosity, and temperature data are used to derive TDS using Archie's Equation, and are then kriged to interpolate TDS. Archie's a and m (tortuosity factor and cementation exponent, respectively) are found by comparing model predictions, after kriging, to TDS measurements, and minimizing the differences via mathematical optimization. Contributions of abundant bicarbonate ions to TDS were corrected using an empirical model. This work was motivated by federal and state law requirements to monitor and protect underground sources of drinking water. Modeling shows the legally significant boundary of 10,000 ppm TDS is at~1,067 m below sea level in Rosedale Ranch, and deepens into Fruitvale to~1,341 m. Mapping groundwater TDS at this resolution reveals that TDS is primarily controlled by depth, recharge, stratigraphy, and in some places, by faulting and facies changes.

Research paper thumbnail of Ancestry-constrained phylogenetic analysis supports the Indo-European steppe hypothesis

Research paper thumbnail of A Relaxed Admixture Model of Language Contact

Language Dynamics and Change, 2014

Under conditions of language contact, a language may gain features from its neighbors that it is ... more Under conditions of language contact, a language may gain features from its neighbors that it is unlikely to have gained endogenously. We describe a method for evaluating pairs of languages for potential contact by comparing a null hypothesis, in which a target language obtained all its features by inheritance, with an alternative hypothesis in which the target language obtained its features via inheritance and via contact with a proposed donor language. Under the alternative hypothesis, the donor may influence the target to gain features, but not to lose features. When applied to a database of phonological characters in South American languages, this method proves useful for detecting the effects of relatively mild and recent contact, and for highlighting several potential linguistic areas in South America.

Research paper thumbnail of Temperature Evolution in a Shallow Aquifer Above a Steamed Heavy-Oil Reservoir in the San Ardo Oil Field, Monterey County, California

Research paper thumbnail of Exploring Phonological Areality in the Circum-Andean Region Using a Naive Bayes Classifier

Quantifying Language Dynamics, 2014

This paper describes the Core and Periphery technique, a quantitative method for exploring areali... more This paper describes the Core and Periphery technique, a quantitative method for exploring areality that uses a naive Bayes classifier, a statistical tool for inferring class membership based on training sets assembled from members of those classes. The Core and Periphery technique is applied to the exploration of phonological areality in the Andes and surrounding lowland regions, based on the South American Phonological Inventory database (SAPhon 1.1.3; Michael, Stark, and Chang 2013). Evidence is found for a phonological area centering on the Andean highlands, and extending to parts of the northern and central Andean foothills regions, the Chaco, and Patagonia. Evidence is also found for Southern and North-Central phonological sub-areas within this larger phonological area.

Research paper thumbnail of Exploring Phonological Areality in the Circum-Andean Region Using a Naive Bayes Classifier

Quantifying Language Dynamics, 2014

This paper describes the Core and Periphery technique, a quantitative method for exploring areali... more This paper describes the Core and Periphery technique, a quantitative method for exploring areality that uses a naive Bayes classifier, a statistical tool for inferring class membership based on training sets assembled from members of those classes. The Core and Periphery technique is applied to the exploration of phonological areality in the Andes and surrounding lowland regions, based on the South American Phonological Inventory database (SAPhon 1.1.3; Michael, Stark, and Chang 2013). Evidence is found for a phonological area centering on the Andean highlands, and extending to parts of the northern and central Andean foothills regions, the Chaco, and Patagonia. Evidence is also found for Southern and North-Central phonological sub-areas within this larger phonological area.

Research paper thumbnail of Mapping aquifer salinity gradients and effects of oil field produced water disposal using geophysical logs: Elk Hills, Buena Vista and Coles Levee Oil Fields, San Joaquin Valley, California

PLOS ONE

The effects of oil and gas production on adjacent groundwater quality are becoming a concern in m... more The effects of oil and gas production on adjacent groundwater quality are becoming a concern in many areas of the United States. As a result, it has become increasingly important to identify which aquifers require monitoring and protection. In this study, we map the extent of groundwater with less than 10,000 mg/L TDS both laterally and vertically near the Elk Hills, Buena Vista and Coles Levee Oil Fields in the San Joaquin Valley, California and note evidence of effects of produced water disposal on salinity within the Tulare aquifer. Subsurface maps showing the depth at which groundwater salinity is less than 10,000 mg/L (or Base 10K) in the Tulare aquifer are generated using geophysical logs and verified by comparison to water sample analyses. The depth to Base 10K ranges from 240 m (800 ft) in Elk Hills to 800 m (2650 ft) in the adjacent Buena Vista syncline and is 670 m (2,200 ft) deep in the Coles Levee area to the east. Log-calculated salinities show a relatively smooth incre...

Research paper thumbnail of Correction: Stratigraphic and structural controls on groundwater salinity variations in the Poso Creek Oil Field, Kern County, California, USA

Hydrogeology Journal

Figure S4 in the electronic supplementary material (ESM) has been replaced to display the correct... more Figure S4 in the electronic supplementary material (ESM) has been replaced to display the correct contours. The original article has been corrected.

Research paper thumbnail of Stratigraphic and structural controls on groundwater salinity variations in the Poso Creek Oil Field, Kern County, California, USA

Hydrogeology Journal

Groundwater total dissolved solids (TDS) distribution was mapped with a three-dimensional (3D) mo... more Groundwater total dissolved solids (TDS) distribution was mapped with a three-dimensional (3D) model, and it was found that TDS variability is largely controlled by stratigraphy and geologic structure. General TDS patterns in the San Joaquin Valley of California (USA) are attributed to predominantly connate water composition and large-scale recharge from the adjacent Sierra Nevada. However, in smaller areas, stratigraphy and faulting play an important role in controlling TDS. Here, the relationship of stratigraphy and structure to TDS concentration was examined at Poso Creek Oil Field, Kern County, California. The TDS model was constructed using produced water TDS samples and borehole geophysics. The model was used to predict TDS concentration at discrete locations in 3D space and used a Gaussian process to interpolate TDS over a volume. In the overlying aquifer, TDS is typically <1,000 mg/L and increases with depth to ~1,200–3,500 mg/L in the hydrocarbon zone below the Macoma cl...

Research paper thumbnail of Groundwater salinity mapping using geophysical log analysis within the Fruitvale and Rosedale Ranch oil fields, Kern County, California, USA

Hydrogeology Journal

A method is presented for deriving a volume model of groundwater total dissolved solids (TDS) fro... more A method is presented for deriving a volume model of groundwater total dissolved solids (TDS) from borehole geophysical and aqueous geochemical measurements. While previous TDS mapping techniques have proved useful in the hydrogeologic setting in which they were developed, they may yield poor results in settings with lithological heterogeneity, complex water chemistry, or limited data. Problems arise because of assumed values for empirical constants in Archie's Equation, unrealistic porosity and temperature gradients, or bicarbonate-rich groundwater. These issues become critical in complex geologic settings such as the San Joaquin Valley of California, USA. To address this, a method to map TDS in three dimensions is applied to the Fruitvale and Rosedale Ranch oil fields near Bakersfield, California. Borehole resistivity, porosity, and temperature data are used to derive TDS using Archie's Equation, and are then kriged to interpolate TDS. Archie's a and m (tortuosity factor and cementation exponent, respectively) are found by comparing model predictions, after kriging, to TDS measurements, and minimizing the differences via mathematical optimization. Contributions of abundant bicarbonate ions to TDS were corrected using an empirical model. This work was motivated by federal and state law requirements to monitor and protect underground sources of drinking water. Modeling shows the legally significant boundary of 10,000 ppm TDS is at~1,067 m below sea level in Rosedale Ranch, and deepens into Fruitvale to~1,341 m. Mapping groundwater TDS at this resolution reveals that TDS is primarily controlled by depth, recharge, stratigraphy, and in some places, by faulting and facies changes.

Research paper thumbnail of Ancestry-constrained phylogenetic analysis supports the Indo-European steppe hypothesis

Research paper thumbnail of A Relaxed Admixture Model of Language Contact

Language Dynamics and Change, 2014

Under conditions of language contact, a language may gain features from its neighbors that it is ... more Under conditions of language contact, a language may gain features from its neighbors that it is unlikely to have gained endogenously. We describe a method for evaluating pairs of languages for potential contact by comparing a null hypothesis, in which a target language obtained all its features by inheritance, with an alternative hypothesis in which the target language obtained its features via inheritance and via contact with a proposed donor language. Under the alternative hypothesis, the donor may influence the target to gain features, but not to lose features. When applied to a database of phonological characters in South American languages, this method proves useful for detecting the effects of relatively mild and recent contact, and for highlighting several potential linguistic areas in South America.