The time-averaged shear wave velocity in the upper 30 m of a site (V s30) is the most common site... more The time-averaged shear wave velocity in the upper 30 m of a site (V s30) is the most common site parameter used in ground motion prediction equations for the evaluation of seismic site response. It is often the case that V s30 is not available at sites with earthquake recordings; for example in the NGA-East site database only 45 of 1149 sites have measured values of V s30. Accordingly, estimates of V s30 are often made on the basis of available proxies that are widely available such as ground slope, geomorphic terrain categories, and surface geology. We compile a database of 1930 measured and inferred V s30 values in Central and Eastern North America (CENA) to test slope and geomorphology-based proxy methods. The results indicate that these existing proxy methods are biased for sites with V s30 greater than 400 m/s. Based on a careful review of geological conditions in the CENA, we propose nineteen geologic classes based on setting (i.e., glaciated or non-glaciated), age, and depositional environmental that can form the basis for geology-based proxy estimates of V s30 as well as for simplified stratigraphic columns.
Bulletin of the Seismological Society of America, 2014
The reference rock site condition is defined by the shear (S)-and compression (P)-wave velocities... more The reference rock site condition is defined by the shear (S)-and compression (P)-wave velocities, as well as a site attenuation parameter (0 ). The significance of the reference rock is that it represents the site condition for which ground motions will be estimated using semi-empirical ground motion prediction equations (GMPEs). Moreover, it is the site condition where site amplification are referenced to (i.e., site amplification is unity for reference rock). This paper presents the recommendation of a reference S-wave velocity, a reference P-wave velocity, and S-wave site attenuation parameter, 0 , associated with a reference rock site condition in Central and Eastern North America (CENA), supported by results of a comprehensive literature search and additional studies. The work is part of the Next Generation Attenuation Relationships for Central and Eastern North America (NGA-East) Project. The recommended Sand P-wave velocities are 3,000 and 5,500 m/sec, respectively. Considering a 5% impact on the site amplification, ranges for the reference Sand P-wave velocities of 2,700 to 3,300 m/sec and 5,000 to 6,100 m/sec, respectively, are recommended. The recommended reference rock site kappa is 0.006 sec. The uncertainty in the site kappa is described using a log-normal distribution with an aleatory standard deviation of 0.43, and epistemic standard deviations of 0.12, when uncertainty in source, path, and site-amplification effects are included in simulations used to develop ground motion prediction equations, and 0.20, when they are not.
In 1976 James Parsons of Mueser Rutledge Consulting Engineers described the engineering character... more In 1976 James Parsons of Mueser Rutledge Consulting Engineers described the engineering characteristics of the varved silts and clays found in the New York City area. Over the years MRCE has conducted extensive testing of the local soils, including work for numerous
In 2006 a boring investigation was conducted at a site in northwest Brooklyn. The project is loca... more In 2006 a boring investigation was conducted at a site in northwest Brooklyn. The project is located along the east side of the East River bounded by N. 5th Street, N. 7th Street, and Kent Avenue. The glacial deposits in the New York City area generally have similar characteristics. They may have the same grain size mix but different colors, or the same color and constituents with slight variations in the grain size range. The borings at this site, however, revealed a complex sequence of strata that included a couple of units that were unusual and distinctive, not typical of anything else in the area. The lead author has spent over the past 20 years with Mueser Rutledge Consulting Engineers sampling, reclassifying and testing soil and rock in the New York City area. In recent years projects in northwest Brooklyn have encountered some of the unusual strata. This particular site brings the distinctive units together in a way that begins to show how they are inter-related. The nature o...
In 1976 James Parsons of Mueser Rutledge Consulting Engineers described the engineering character... more In 1976 James Parsons of Mueser Rutledge Consulting Engineers described the engineering characteristics of the varved silts and clays found in the New York City area. Over the years MRCE has conducted extensive testing of the local soils, including work for numerous NYC housing projects, which was the source for much of Parsons’ data. The test programs included consolidation tests. A consolidation test can be used to determine the maximum load to which a given soil has been subjected. In his study, Parsons determined that the varved soils of New York City were highly overconsolidated, meaning that the sediments had settled under weights significantly greater than the present overburden. He concluded that, although there was no known visible geologic evidence of later glacial advances, a younger advance was the only way to explain such high loads over an area.
Hurricane Sandy was the deadliest and most destructive event of the 2012 Atlantic hurricane seaso... more Hurricane Sandy was the deadliest and most destructive event of the 2012 Atlantic hurricane season. It originated as a storm off the coast of West Africa that turned into a tropical wave in the southwestern Caribbean Sea, and then into a hurricane that moved slowly north along the United States East Coast. Numerous regional coastal communities and urban centers in New Jersey (NJ) and the New York City (NYC) metropolitan area experienced widespread flooding, extreme winds, and heavy damage that disrupted daily life and business in Lower Manhattan, the world’s financial capital. Consequences with great geotechnical engineering interest include: (i) modification of the regional coastal geomorphology due to storm surge, with the birth of new inlets, erosion, scour of soil at the shorelines; (ii) damage in coastal communities that revealed the vulnerability of residential building foundations not designed according to modern flood protection standards; and (iii) interruption of service o...
Then the world’s tallest buildings, the former World Trade Center Twin Towers were built in lower... more Then the world’s tallest buildings, the former World Trade Center Twin Towers were built in lower Manhattan in the early 1970’s. A new construction technology at the time, a slurry wall socketed into the bedrock was built to enable the Twin Towers construction. A geotechnical investigation undertaken for the project suggested that the site geology would be fairly typical for New York City. During construction of the slurry wall, however, an unexpected feature was discovered. In the southeast corner of the site the wall cut through a ledge of schistose bedrock and entered a curved, roughly E-W-trending valley filled with wellrounded glacial boulders and cobbles (Figure 1). The slurry wall had to be excavated deeper in two places to get through the boulders and socket back into solid bedrock. The trend of the valley is unusual because other known glacial valleys across Manhattan trend NW-SE including a nearby valley we reported on earlier (Moss and Merguerian 2006).
Over the past three years we have been examining drill core that has penetrated bedrock from vari... more Over the past three years we have been examining drill core that has penetrated bedrock from various construction sites throughout NYC. Careful examination of rock core, sampling, and petrography have been fruitful in extending mapping to southern Manhattan from areas of natural exposures north of 59 Street. The outcrop and drill core data support the view that at least three distinctly different and mappable schistose units constitute the formation known as the Manhattan Schist. Separated by ductile faults known as the St. Nicholas thrust and Cameron’s Line the schistose rocks, from their structural base upwards, are known as the autochthonous Walloomsac formation and allochthonous Manhattan and Hartland formations.
Our field and subsurface studies of glacial strata from construction sites and borings indicate t... more Our field and subsurface studies of glacial strata from construction sites and borings indicate that the glacial history of the New York City area is complex. The Ronkonkoma and Harbor Hill terminal moraines are evidence that the area has experienced more than one glacial advance. There is more to the story, however, than simply ice advance, retreat, repeat. Many locations in New York City display seemingly simple stratigraphy, such as thick layers of till over bedrock or 100’ of outwash sands. Most sites aren’t as obviously complex as one offering multiple tills intercalated with outwash and varved strata. When characteristics other than soil type are taken into consideration, however, stratigraphic differences sometimes appear. A change in color or mineralogy, for instance, might indicate ice coming from another direction. A change in engineering properties can also contribute to the art of unraveling glacial history.
Until the 1980’s, geologic mapping in the New York City area identified 3 different major rock fo... more Until the 1980’s, geologic mapping in the New York City area identified 3 different major rock formations – the Fordham Gneiss, the Inwood Marble (formerly Limestone) and schistose rock previously called Hudson Schist, more recently Manhattan Schist. With the advent of plate tectonics, the Manhattan Formation was progressively divided into 3 structurally and lithologically separate formations – the Walloomsac, Manhattan and Hartland (Merguerian 2008, Merguerian and Sanders 1991b). While generally schistose in nature with overlapping characteristics, these 3 formations have differences, due largely to their origins, which can significantly affect the engineering properties of the rock.
The time-averaged shear wave velocity in the upper 30 m of a site (V s30) is the most common site... more The time-averaged shear wave velocity in the upper 30 m of a site (V s30) is the most common site parameter used in ground motion prediction equations for the evaluation of seismic site response. It is often the case that V s30 is not available at sites with earthquake recordings; for example in the NGA-East site database only 45 of 1149 sites have measured values of V s30. Accordingly, estimates of V s30 are often made on the basis of available proxies that are widely available such as ground slope, geomorphic terrain categories, and surface geology. We compile a database of 1930 measured and inferred V s30 values in Central and Eastern North America (CENA) to test slope and geomorphology-based proxy methods. The results indicate that these existing proxy methods are biased for sites with V s30 greater than 400 m/s. Based on a careful review of geological conditions in the CENA, we propose nineteen geologic classes based on setting (i.e., glaciated or non-glaciated), age, and depositional environmental that can form the basis for geology-based proxy estimates of V s30 as well as for simplified stratigraphic columns.
Bulletin of the Seismological Society of America, 2014
The reference rock site condition is defined by the shear (S)-and compression (P)-wave velocities... more The reference rock site condition is defined by the shear (S)-and compression (P)-wave velocities, as well as a site attenuation parameter (0 ). The significance of the reference rock is that it represents the site condition for which ground motions will be estimated using semi-empirical ground motion prediction equations (GMPEs). Moreover, it is the site condition where site amplification are referenced to (i.e., site amplification is unity for reference rock). This paper presents the recommendation of a reference S-wave velocity, a reference P-wave velocity, and S-wave site attenuation parameter, 0 , associated with a reference rock site condition in Central and Eastern North America (CENA), supported by results of a comprehensive literature search and additional studies. The work is part of the Next Generation Attenuation Relationships for Central and Eastern North America (NGA-East) Project. The recommended Sand P-wave velocities are 3,000 and 5,500 m/sec, respectively. Considering a 5% impact on the site amplification, ranges for the reference Sand P-wave velocities of 2,700 to 3,300 m/sec and 5,000 to 6,100 m/sec, respectively, are recommended. The recommended reference rock site kappa is 0.006 sec. The uncertainty in the site kappa is described using a log-normal distribution with an aleatory standard deviation of 0.43, and epistemic standard deviations of 0.12, when uncertainty in source, path, and site-amplification effects are included in simulations used to develop ground motion prediction equations, and 0.20, when they are not.
In 1976 James Parsons of Mueser Rutledge Consulting Engineers described the engineering character... more In 1976 James Parsons of Mueser Rutledge Consulting Engineers described the engineering characteristics of the varved silts and clays found in the New York City area. Over the years MRCE has conducted extensive testing of the local soils, including work for numerous
In 2006 a boring investigation was conducted at a site in northwest Brooklyn. The project is loca... more In 2006 a boring investigation was conducted at a site in northwest Brooklyn. The project is located along the east side of the East River bounded by N. 5th Street, N. 7th Street, and Kent Avenue. The glacial deposits in the New York City area generally have similar characteristics. They may have the same grain size mix but different colors, or the same color and constituents with slight variations in the grain size range. The borings at this site, however, revealed a complex sequence of strata that included a couple of units that were unusual and distinctive, not typical of anything else in the area. The lead author has spent over the past 20 years with Mueser Rutledge Consulting Engineers sampling, reclassifying and testing soil and rock in the New York City area. In recent years projects in northwest Brooklyn have encountered some of the unusual strata. This particular site brings the distinctive units together in a way that begins to show how they are inter-related. The nature o...
In 1976 James Parsons of Mueser Rutledge Consulting Engineers described the engineering character... more In 1976 James Parsons of Mueser Rutledge Consulting Engineers described the engineering characteristics of the varved silts and clays found in the New York City area. Over the years MRCE has conducted extensive testing of the local soils, including work for numerous NYC housing projects, which was the source for much of Parsons’ data. The test programs included consolidation tests. A consolidation test can be used to determine the maximum load to which a given soil has been subjected. In his study, Parsons determined that the varved soils of New York City were highly overconsolidated, meaning that the sediments had settled under weights significantly greater than the present overburden. He concluded that, although there was no known visible geologic evidence of later glacial advances, a younger advance was the only way to explain such high loads over an area.
Hurricane Sandy was the deadliest and most destructive event of the 2012 Atlantic hurricane seaso... more Hurricane Sandy was the deadliest and most destructive event of the 2012 Atlantic hurricane season. It originated as a storm off the coast of West Africa that turned into a tropical wave in the southwestern Caribbean Sea, and then into a hurricane that moved slowly north along the United States East Coast. Numerous regional coastal communities and urban centers in New Jersey (NJ) and the New York City (NYC) metropolitan area experienced widespread flooding, extreme winds, and heavy damage that disrupted daily life and business in Lower Manhattan, the world’s financial capital. Consequences with great geotechnical engineering interest include: (i) modification of the regional coastal geomorphology due to storm surge, with the birth of new inlets, erosion, scour of soil at the shorelines; (ii) damage in coastal communities that revealed the vulnerability of residential building foundations not designed according to modern flood protection standards; and (iii) interruption of service o...
Then the world’s tallest buildings, the former World Trade Center Twin Towers were built in lower... more Then the world’s tallest buildings, the former World Trade Center Twin Towers were built in lower Manhattan in the early 1970’s. A new construction technology at the time, a slurry wall socketed into the bedrock was built to enable the Twin Towers construction. A geotechnical investigation undertaken for the project suggested that the site geology would be fairly typical for New York City. During construction of the slurry wall, however, an unexpected feature was discovered. In the southeast corner of the site the wall cut through a ledge of schistose bedrock and entered a curved, roughly E-W-trending valley filled with wellrounded glacial boulders and cobbles (Figure 1). The slurry wall had to be excavated deeper in two places to get through the boulders and socket back into solid bedrock. The trend of the valley is unusual because other known glacial valleys across Manhattan trend NW-SE including a nearby valley we reported on earlier (Moss and Merguerian 2006).
Over the past three years we have been examining drill core that has penetrated bedrock from vari... more Over the past three years we have been examining drill core that has penetrated bedrock from various construction sites throughout NYC. Careful examination of rock core, sampling, and petrography have been fruitful in extending mapping to southern Manhattan from areas of natural exposures north of 59 Street. The outcrop and drill core data support the view that at least three distinctly different and mappable schistose units constitute the formation known as the Manhattan Schist. Separated by ductile faults known as the St. Nicholas thrust and Cameron’s Line the schistose rocks, from their structural base upwards, are known as the autochthonous Walloomsac formation and allochthonous Manhattan and Hartland formations.
Our field and subsurface studies of glacial strata from construction sites and borings indicate t... more Our field and subsurface studies of glacial strata from construction sites and borings indicate that the glacial history of the New York City area is complex. The Ronkonkoma and Harbor Hill terminal moraines are evidence that the area has experienced more than one glacial advance. There is more to the story, however, than simply ice advance, retreat, repeat. Many locations in New York City display seemingly simple stratigraphy, such as thick layers of till over bedrock or 100’ of outwash sands. Most sites aren’t as obviously complex as one offering multiple tills intercalated with outwash and varved strata. When characteristics other than soil type are taken into consideration, however, stratigraphic differences sometimes appear. A change in color or mineralogy, for instance, might indicate ice coming from another direction. A change in engineering properties can also contribute to the art of unraveling glacial history.
Until the 1980’s, geologic mapping in the New York City area identified 3 different major rock fo... more Until the 1980’s, geologic mapping in the New York City area identified 3 different major rock formations – the Fordham Gneiss, the Inwood Marble (formerly Limestone) and schistose rock previously called Hudson Schist, more recently Manhattan Schist. With the advent of plate tectonics, the Manhattan Formation was progressively divided into 3 structurally and lithologically separate formations – the Walloomsac, Manhattan and Hartland (Merguerian 2008, Merguerian and Sanders 1991b). While generally schistose in nature with overlapping characteristics, these 3 formations have differences, due largely to their origins, which can significantly affect the engineering properties of the rock.
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Papers by Cheryl Moss