摘要:

A Bayesian procedure for examining whether the time-space variation of the magnitudefrequency relation conforms with the exponential distribution or not is proposed. The relation in each time-space segment is obtained as a histogram. The smoothness of the estimated histogram is guaranteed by the introduction of prior distributions of the parameters in time, space, and magnitude. The parameters of the prior distribution are chosen to minimise Akaike's Bayesian Information Criterion (ABIC). This procedure is applied to three earthquake catalogues in New Zealand: those for the Wellington Seismograph Network, the Pukaki Network, and the New Zealand Network respectively. For both the Wellington and Pukaki Networks, departure from the exponential distribution is the main effect and the time variation is secondary. For the New Zealand Network, where the magnitude- frequency relation appears to be an exponential distribution, the variation of b over time and space suggests a relation between periods of active seismicity and periods of high b-value, not locally, but overall in the main seismic region.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10422177

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Copland and Cook River Valleys provide a cross-section through the 25 km wide, pum-pellyite-actinolite to amphibolite facies Alpine schists along the Indian/Pacific plates boundary in South Island, New Zealand. Five phases of deformation are reported: D1, possible soft-sediment folding; D2, syn-first metamorphic isoclinal folds; D3, syn-second metamorphic regional folds; D., local upright folds; D5, faulting. The D3structures include vertically and laterally anastomosing late D3 domains of intense transposition (Paringa domains). The D3 structures formed during mid Tertiary to Late Miocene times in response to broadly. distributed dextral transpressive strain along the Indian/Pacific plates' boundary. This strain was localised later to the Alpine Fault. The D3 structural style changes south of Moeraki Valley, and reflects the change in dip of the plate boundary, from steeply east-dipping in the study area, to shallowly east-dipping south of Moeraki Valley.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10422178

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Abundant xenoliths of metasedimentary origin in lavas of Tongariro Volcanic Centre (New Zealand) are of three main types. Quartz-rich xenoliths are conspicuous in most lavas and include rare garnet-bearing schists and more abundant metaquartzites. The latter represent restites of garnet- schist modified by extraction of granitic partial melt. Feldspar-rich xenoliths occur in subequal abundance to quartz-rich xenoliths and include biotite-schists and pyroxene-hornfelses. The latter represent restites after extraction of partial melt from biotite-schist. Uncommon (but widespread) spinel-rich xenoliths also occur. All of the above xenolith types were derived from Torlesse terrane greywacke, regionally metamorphosed to gneiss. They represent the quartzose, feldspathic, and micaceous layers of gneiss, thermally disaggregated following immersion in host lava. The dominance of restite assemblages (i.e., metaquartzites and pyroxene-hornfelses) testifies to the widespread production, extraction, and assimilation of granitic partial melts of xenoliths with host magmas.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10422179

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Trends of radial dikes of the Miocene Lyttelton Volcano, Banks Peninsula, New Zealand, indicate two principal centres of activity—one in Head of the Bay, the other in Charteris Bay—here namedLytteiton 1andLyttelton 2respectively. Crosscutting dikes indicate Lyttelton 2 is the younger centre. The circular eroded crater rim of Lyttelton Volcano is related to Lyttelton 2, supporting the later date for that centre, but drainage on the outer slopes is inherited from a pattern consequent to Lyttelton 1. Lyttelton 2 deposits effectively blanket those of Lyttelton I, but Lyttelton I deposits are clearly seen above Governors Bay where they dip away from Head of the Bay and make angles of up to 20° with the present crater rim. Taking into account the pre-Lyttelton Governors Bay Volcanics, the locus of activity from before 12 Ma to about 10 Ma ago migrated in a northeasterly direction, at right angles to the later migration from Lyttelton to Akaroa.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10422180

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Glacial outwash aggradation terrace surfaces in North Westland form suitable reference surfaces for showing Quaternary deformation, which increases in keeping with increasing age of surface and varies in relation to the regional structure of Tertiary rocks.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10422181

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Location of an estuarine bed near Opiki enabled the approximate mid Holocene limit of the Manawatu River estuary to be determined. Since about 6000 years B.P., flood-plain accretion in that area has averaged 1.5 mm/year, although accretion rates may have diminished with time. Two riverbank sections near Rangiotu provide evidence for the initial encroachment of Foxton Phase dunes. Thin sand horizons overlying the former flood-plain surface are identified as eolian veneer deposits, preserved at the rear of former migrating dunes, which constructed sand plains. Radiocarbon dates obtained from interbedded organic material reveal that dunes first entered the area c. 2300 years B.P. with further episodic encroachment until c. 1600 years B.P. As the Foxton Phase dunes had migrated c. 16 km inland there is no absolute date for the commencement of the phase but study of contemporary rates of dun~ advance suggests that the Foxton Phase may have been initiated at the coast about 550~6oo0 calendar years ago.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10422182

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The eastern areas of the South Island of New Zealand have marked rainfall variability. There has been, from time to time, interest in augmenting rainfall by artificial methods. Using recorded rainfall, numerical experiments are conducted to determine by Monte Carlo methods the probability of statistically detecting particular rainfall increases in experiments lasting 5 or 10 years and conducted over the November-April period. A rainfall increase of 30% on seeded occasions would probably be detected but smaller increases might not be identifiable even in 10 years. Restriction of seeding to occasions when there is a large water need has little effect on the probability of detecting effects of seeding.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10422183

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The Southern Oscillation index (SOl) and rainfall indices at three South Pacific island groups are found to be significantly and inversely related, with the SOl leading by several months.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10422184

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Analyses of samples of iron-manganese concretions and their surrounding soil materials, from a catenary sequence of four yellowgrey earth soils (two Fragiaquepts and two Fragiochrepts) near Allanton, have been carried out using spark source mass spectrometry. Data are presented for 12 rare earth elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb) and 5 others (U, Th, Pb, Cs, and As). The rare earth elements show little or no enrichment in the concretions relative to the surrounding soil and this is consistent with a relatively low degree of enrichment of Mn in the concretions. As, Pb, and Th are enriched in all samples of concretions.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10422185

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Two occurrences of lawsonite-bearing veins in Torlesse greywacke and metabasite from the coastal area of Wellington Peninsula are described. Lawsonite is previously undescribed from the Torlesse terrane. Its presence indicates higher pressure conditions of metamorphism, corresponding to the lawsonite-albite-chlorite facies, than is generally observed in Torlesse rocks.

ISSN:0028-8306    

DOI:10.1080/00288306.1987.10422186

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor