title: Paleoliquefaction in Late Pleistocene alluvial sediments in the Hauraki and Hamilton basins

authors: Kleyburg, Melissa Anita

subjects: paleoliquefaction

abstract: Liquefaction susceptibility of the Late Pleistocene Hinuera Formation volcanogenic sediments is of interest to the engineering community as it is unclear whether materials of this age will still be prone to activation by cyclic stresses. Screening methods suggest a low susceptibility to liquefaction, yet instrumental tools such as Cone Penetrometer Tests (CPT) imply a much greater susceptibility. Recognising paleoliquefaction features in the geological record provides evidence of paleoseismicity.

The Hinuera Formation was deposited by an active braided alluvial system of the ancestral Waikato River during the late Pleistocene, with the bulk of sediments located in the Hauraki Basin (deposited before c. 22,000 calendar years ago) and in the Hamilton Basin (deposited mainly c. 22,000 to c. 18,000 calendar years ago). Lithofacies in the Hinuera Formation include unconsolidated gravels, gravelly sands, sands, and silts, with interbedded peats. The deposits are complex structurally both laterally and vertically because of the migration of channels laterally during low-angle fan-building. Previous studies on post-sedimentary features of the Hinuera Formation identified uncommon secondary sedimentary structures that at the time were of uncertain origin, either from non-seismic or seismic triggers.

Excavations into the Hinuera Formation at two sites showed definitive evidence of paleoliquefaction features: a sand quarry on Aspin Road (site 15) and Endeavour Primary School (site 16). These sites showed earthquake-induced injection structures (sand dikes) intruding through several lithological layers, including an organic layer. Through cross-cutting relationships, maximum age of occurrence for the injection structures are determined. A seismic event causing liquefaction occurred sometime after c. 20,749 ± 204 calendar years ago (95% probability range) at site 15 and after c. 19,964 ± 222 calendar years ago (95% probability range) at site 16.

The instrumental CPT data provides a valid method of predicting liquefaction potential. However, the sedimentary materials are highly variable over short distances and so liquefaction is therefore localised; it is difficult to infer ground conditions more than a few metres from a CPT site without further ground-truth information. Sites of known paleoliquefaction features show Factor of Safety (FS) values of 0.25 to 0.5 for the critical layers, these are values that predict liquefaction. Liquefaction Potential Index (LPI) values that are calculated present high risks of liquefaction occurring and calculated liquefaction severity number (LSN) values show minor to moderate expression of liquefaction. Field observations and CPTu based predicted liquefaction are therefore in keeping.

Key conditions observed at the two sites with identified paleoliquefaction features included the presence of silts associated with organic-rich materials. High levels of organic material reflect impeded or slow flowing drainage associated with overbank silt deposition, and thus are indicative of the elevated water tables required for liquefaction. The liquefaction structures observed are both at locations where the modern (pedological) soils (Te Rapa and Te Kowhai soil series) occurred in topographic depressions on the Hinuera Surface. Therefore this relationship enabled the development of a soil-landscape model using the modern soil pattern to tentatively predict, areas of higher susceptibility to liquefaction.

text: Paleoliquefaction in Late Pleistocene alluvial sediments in the Hauraki and Hamilton basins Liquefaction susceptibility of the Late Pleistocene Hinuera Formation volcanogenic sediments is of interest to the engineering community as it is unclear whether materials of this age will still be prone to activation by cyclic stresses. Screening methods suggest a low susceptibility to liquefaction, yet instrumental tools such as Cone Penetrometer Tests (CPT) imply a much greater susceptibility. Recognising paleoliquefaction features in the geological record provides evidence of paleoseismicity.

The Hinuera Formation was deposited by an active braided alluvial system of the ancestral Waikato River during the late Pleistocene, with the bulk of sediments located in the Hauraki Basin (deposited before c. 22,000 calendar years ago) and in the Hamilton Basin (deposited mainly c. 22,000 to c. 18,000 calendar years ago). Lithofacies in the Hinuera Formation include unconsolidated gravels, gravelly sands, sands, and silts, with interbedded peats. The deposits are complex structurally both laterally and vertically because of the migration of channels laterally during low-angle fan-building. Previous studies on post-sedimentary features of the Hinuera Formation identified uncommon secondary sedimentary structures that at the time were of uncertain origin, either from non-seismic or seismic triggers.

Excavations into the Hinuera Formation at two sites showed definitive evidence of paleoliquefaction features: a sand quarry on Aspin Road (site 15) and Endeavour Primary School (site 16). These sites showed earthquake-induced injection structures (sand dikes) intruding through several lithological layers, including an organic layer. Through cross-cutting relationships, maximum age of occurrence for the injection structures are determined. A seismic event causing liquefaction occurred sometime after c. 20,749 ± 204 calendar years ago (95% probability range) at site 15 and after c. 19,964 ± 222 calendar years ago (95% probability range) at site 16.

The instrumental CPT data provides a valid method of predicting liquefaction potential. However, the sedimentary materials are highly variable over short distances and so liquefaction is therefore localised; it is difficult to infer ground conditions more than a few metres from a CPT site without further ground-truth information. Sites of known paleoliquefaction features show Factor of Safety (FS) values of 0.25 to 0.5 for the critical layers, these are values that predict liquefaction. Liquefaction Potential Index (LPI) values that are calculated present high risks of liquefaction occurring and calculated liquefaction severity number (LSN) values show minor to moderate expression of liquefaction. Field observations and CPTu based predicted liquefaction are therefore in keeping.

Key conditions observed at the two sites with identified paleoliquefaction features included the presence of silts associated with organic-rich materials. High levels of organic material reflect impeded or slow flowing drainage associated with overbank silt deposition, and thus are indicative of the elevated water tables required for liquefaction. The liquefaction structures observed are both at locations where the modern (pedological) soils (Te Rapa and Te Kowhai soil series) occurred in topographic depressions on the Hinuera Surface. Therefore this relationship enabled the development of a soil-landscape model using the modern soil pattern to tentatively predict, areas of higher susceptibility to liquefaction.

year: 2015

title: Exploring mood in neverver

authors: Barbour, Julie Renee

subjects: mood

abstract: In a preverbal position, all clauses in the Neverver language of Malakula Island (Vanuatu) are either unmarked, or carry the morpheme m- prefixed to the verb. In this paper, I explore the distribution of unmarked and mmarked clauses, examining a number of semantic and grammatical contexts. I seek to establish whether the choice of using an unmarked clause or an m-marked clause is driven by the temporal location of the situation expressed in the clause, or by the status of that situation in reality. In doing so, I aim to test my earlier analysis of Neverver as being a mood language. The results, however, are divided, with temporal location appearing to be more salient in some contexts, and reality status appearing to be more salient in others. Relying predominantly on evidence from a variety of subordinate clause types, I maintain that Neverver is indeed a mood language, although an interpretation of the same morphological category as grammatical tense is certainly plausible in some contexts.

text: Exploring mood in neverver In a preverbal position, all clauses in the Neverver language of Malakula Island (Vanuatu) are either unmarked, or carry the morpheme m- prefixed to the verb. In this paper, I explore the distribution of unmarked and mmarked clauses, examining a number of semantic and grammatical contexts. I seek to establish whether the choice of using an unmarked clause or an m-marked clause is driven by the temporal location of the situation expressed in the clause, or by the status of that situation in reality. In doing so, I aim to test my earlier analysis of Neverver as being a mood language. The results, however, are divided, with temporal location appearing to be more salient in some contexts, and reality status appearing to be more salient in others. Relying predominantly on evidence from a variety of subordinate clause types, I maintain that Neverver is indeed a mood language, although an interpretation of the same morphological category as grammatical tense is certainly plausible in some contexts.

year: 2011-06

title: Environmental aspects of storm runoff discharge from a timber port, Tauranga, New Zealand

authors: Tian, Fengming

subjects: storm runoff water

abstract: An investigation was undertaken into storm runoff water quantity and quality, contaminant input to the receiving tidal waters from the Mt. Maunganui wharf, accumulation of potentially toxic resin acids in adjacent sediments, and the dilution of the wharf runoff in the receiving tidal waters, in order to assess the possible adverse environmental impact associated with the log operation at the Port of Tauranga Ltd.
Based upon field data and rainfall records, about a half of the annual precipitation over the log handling areas is converted to surface runoff (117,000 m³a⁻¹). Annual runoff volume per hectare of wharf surface is estimated as 7,500 m³ha⁻¹a⁻¹ for the sealed area and 3,700 m³ha⁻¹a⁻¹ for the gravelled area.
The optical quality of the wharf runoff is degraded due to addition of bark and soil particles. The black disk visual clarity (0.01-0.02 m) was only 0.5-1.0% of that in the receiving tidal waters. The wharf runoff appears very dark gray to yellowish brown in apparent colour (10YR1/3 to 10YR5/6 Munsell colour chart) and has a soluble yellow substance concentration of about 25 m⁻¹. Power relationships between the traditionally used parameters, for example, suspended solids and turbidity, were identified. The wharf surface pavement types had a significant influence on visual clarity, but little influence on yellow substance concentration.
The potentially toxic resin acids in the wharf runoff have been determined with SIM GC-MS. The average total resin acid level (1,030 ppb) is comparable to that of 1,000 ppb reported at which acute toxicity is likely to be exhibited. A relationship of resin acids against volatile suspended solids was established. Tests undertaken suggest that conventional treatment methods of natural sedimentation and flocculation-sedimentation are able to remove the resin acids effectively.
The levels of biological oxygen demand (BOD), total phosphorus and nitrogen in the wharf runoff are considerably higher than those of common urban runoff. However, the wharf runoff contributes little nitrate nitrogen and oil and grease to the receiving environment.
About 87,500 kg of suspended solids, 43,000 kg of volatile suspended solids, 14,200 kg of BOD, 500 kg of phosphorus, and 103 kg of resin acids are discharged to the Tauranga Harbour annually from runoff from the Mt. Maunganui wharf.
Analyses show that the impact on adjacent sediments from the storm runoff is limited to a distance of about 100 m from the discharge points and the resin acid levels in the sediments within this distance are not significantly higher compared to that of the storm runoff. The net resin acid accumulation rate in the shipping channel (Stella Passage) beside the log handling areas was estimated to be in the range of 300 to 370 ppb per year.
Based on field investigation and numerical simulations, the findings on dispersion and dilution of the wharf runoff in the receiving tidal waters are as follows: (i) the sea water around Stella Passage experiences an obvious natural salinity stratification, the extent of which depends greatly on the weather conditions; (ii) the wind drag stress and the pressure gradient caused by the addition of runoff had the greatest influence on the plume dynamics during the flood tide. The plumes basically remain within the top 2-3 m of the water column under different winds; (iii) the plume is unlikely to advect to the Whareroa Marae under strong (30-40 knots) easterly or northeasterly winds for a storm with a 5-year return period. However, there is an obvious influence on the Whareroa Marae under 30- 40 knot northerly winds; and (iv) the short duration and restricted region of the low dilution pulse of effluent around slack water may explain why there has been no reports of acute toxic events.
Sealing the gravel covered wharf area, improving the sweeping efficiency, and extending the present outfalls to the sea floor might be potential options for mitigating the environmental impact associated with discharge of the wharf runoff.

text: Environmental aspects of storm runoff discharge from a timber port, Tauranga, New Zealand An investigation was undertaken into storm runoff water quantity and quality, contaminant input to the receiving tidal waters from the Mt. Maunganui wharf, accumulation of potentially toxic resin acids in adjacent sediments, and the dilution of the wharf runoff in the receiving tidal waters, in order to assess the possible adverse environmental impact associated with the log operation at the Port of Tauranga Ltd.
Based upon field data and rainfall records, about a half of the annual precipitation over the log handling areas is converted to surface runoff (117,000 m³a⁻¹). Annual runoff volume per hectare of wharf surface is estimated as 7,500 m³ha⁻¹a⁻¹ for the sealed area and 3,700 m³ha⁻¹a⁻¹ for the gravelled area.
The optical quality of the wharf runoff is degraded due to addition of bark and soil particles. The black disk visual clarity (0.01-0.02 m) was only 0.5-1.0% of that in the receiving tidal waters. The wharf runoff appears very dark gray to yellowish brown in apparent colour (10YR1/3 to 10YR5/6 Munsell colour chart) and has a soluble yellow substance concentration of about 25 m⁻¹. Power relationships between the traditionally used parameters, for example, suspended solids and turbidity, were identified. The wharf surface pavement types had a significant influence on visual clarity, but little influence on yellow substance concentration.
The potentially toxic resin acids in the wharf runoff have been determined with SIM GC-MS. The average total resin acid level (1,030 ppb) is comparable to that of 1,000 ppb reported at which acute toxicity is likely to be exhibited. A relationship of resin acids against volatile suspended solids was established. Tests undertaken suggest that conventional treatment methods of natural sedimentation and flocculation-sedimentation are able to remove the resin acids effectively.
The levels of biological oxygen demand (BOD), total phosphorus and nitrogen in the wharf runoff are considerably higher than those of common urban runoff. However, the wharf runoff contributes little nitrate nitrogen and oil and grease to the receiving environment.
About 87,500 kg of suspended solids, 43,000 kg of volatile suspended solids, 14,200 kg of BOD, 500 kg of phosphorus, and 103 kg of resin acids are discharged to the Tauranga Harbour annually from runoff from the Mt. Maunganui wharf.
Analyses show that the impact on adjacent sediments from the storm runoff is limited to a distance of about 100 m from the discharge points and the resin acid levels in the sediments within this distance are not significantly higher compared to that of the storm runoff. The net resin acid accumulation rate in the shipping channel (Stella Passage) beside the log handling areas was estimated to be in the range of 300 to 370 ppb per year.
Based on field investigation and numerical simulations, the findings on dispersion and dilution of the wharf runoff in the receiving tidal waters are as follows: (i) the sea water around Stella Passage experiences an obvious natural salinity stratification, the extent of which depends greatly on the weather conditions; (ii) the wind drag stress and the pressure gradient caused by the addition of runoff had the greatest influence on the plume dynamics during the flood tide. The plumes basically remain within the top 2-3 m of the water column under different winds; (iii) the plume is unlikely to advect to the Whareroa Marae under strong (30-40 knots) easterly or northeasterly winds for a storm with a 5-year return period. However, there is an obvious influence on the Whareroa Marae under 30- 40 knot northerly winds; and (iv) the short duration and restricted region of the low dilution pulse of effluent around slack water may explain why there has been no reports of acute toxic events.
Sealing the gravel covered wharf area, improving the sweeping efficiency, and extending the present outfalls to the sea floor might be potential options for mitigating the environmental impact associated with discharge of the wharf runoff.

year: 1997