The Effect of Catalogue Lead Time on Medium-Term Earthquake Forecasting with Application to New Zealand Data.

'Every Earthquake a Precursor According to Scale' (EEPAS) is a catalogue-based model to forecast earthquakes within the coming months, years and decades, depending on magnitude. EEPAS has been shown to perform well in seismically active regions like New Zealand (NZ). It is based on the observation that seismicity increases prior to major earthquakes. This increase follows predictive scaling relations. For larger target earthquakes, the precursor time is longer and precursory seismicity may have occurred prior to the start of the catalogue. Here, we derive a formula for the completeness of precursory earthquake contributions to a target earthquake as a function of its magnitude and lead time, where the lead time is the length of time from the start of the catalogue to its time of occurrence. We develop two new versions of EEPAS and apply them to NZ data. The Fixed Lead time EEPAS (FLEEPAS) model is used to examine the effect of the lead time on forecasting, and the Fixed Lead time Compensated EEPAS (FLCEEPAS) model compensates for incompleteness of precursory earthquake contributions. FLEEPAS reveals a space-time trade-off of precursory seismicity that requires further investigation. Both models improve forecasting performance at short lead times, although the improvement is achieved in different ways.

Legislation reduces exposure to second-hand tobacco smoke in New Zealand bars by about 90%.

AIM: To measure exposure to second-hand smoke (SHS) in New Zealand bars before and after comprehensive smoke-free legislation enacted on 10 December 2004. METHODS: Cotinine is the main specific metabolite of nicotine and a well-established biomarker for SHS exposure. We measured cotinine levels in saliva of non-smoking volunteers before and after a 3 h visit to 30 randomly selected bars in 3 cities across the country. Two measures of cotinine before the smoke-free law change during winter and spring 2004, and two follow-up measurements in the same volunteers and venues during winter and spring 2005, were included. RESULTS: Before the smoke-free law change, in all bars and in all volunteers, exposure to SHS was evident with an average increase in saliva cotinine of 0.66 ng/ml (SE 0.03 ng/ml). Increases in cotinine correlated strongly with the volunteers' subjective observation of ventilation, air quality and counts of lit cigarettes. However, even venues that were judged to be "seemingly smoke free" with "good ventilation" produced discernable levels of SHS exposure. After the law change, there remained some exposure to SHS, but at much lower levels (mean saliva cotinine increase of 0.08 ng/ml, SE 0.01 ng/ml). Smoking indoors in bars was almost totally eliminated: in 2005 only one lit cigarette was observed in 30 visits. CONCLUSIONS: Comprehensive smoke-free legislation in New Zealand seems to have reduced exposure of bar patrons to SHS by about 90%. Residual exposures to SHS in bars do not result from illicit smoking indoors.

Secondhand tobacco smoke exposure in New Zealand bars: results prior to implementation of the bar smoking ban.

AIMS: To measure secondhand smoke (SHS) levels in New Zealand bars prior to smokefree legislation enacted on 10 December 2004. METHODS: Thirty bars were randomly selected from urban, surburban, and surrounding rural areas of Auckland, Wellington, and Invercargill. Bars were visited (on a Friday or Saturday night for a 3-hour stay between 1800 and 2400 hours) in July/August/September 2004 (winter) and again in October/November 2004 (spring). Each bar was visited by a group of 4 or 5 non-smokers participating in the study. All groups of participants spent a 3-hour block of continuous time in the bar. Saliva samples (approximately 0.5-2 mL) were provided immediately prior to entering the bar as well as 5-15 minutes after leaving the bar. Each group recorded the initial impression of air quality and ventilation, the number of observed lit cigarettes over three 10-minute intervals throughout the evening, and the number of patrons at each interval. In addition, any general comments about the venue (relevant to bar attendance or air quality on the evening) was recorded. Cotinine, the main metabolite of nicotine, was measured in saliva samples using Liquid Chromatography with tandem Mass Spectrometry (LC-MS-MS). RESULTS: In all bars, and in all volunteers, exposure to SHS was evident. Saliva cotinine increased after 3 hours in the bar (mean increase=0.66 ng/mL, SE=0.03 ng/mL, p value of <0.0001). The 30 bars randomly selected provided a good spectrum of SHS exposures, with mean cotinine increasing by approximately 8-fold. Smaller population centres showed greater exposures to SHS. A north-south gradient of exposure was also seen (highest exposures were in Southland). Higher exposures were seen in the winter than in the spring. The objective measures of SHS exposure correlated strongly with the volunteers' subjective observation of ventilation, air quality, and counts of lit cigarettes. One exception was where objective salivary markers indicated that even "seemingly smokefree" venues with "good ventilation" produced discernable levels of SHS exposure. CONCLUSIONS: We have utilised an objective, non-invasive scientific approach to assess SHS smoke exposure in patrons of New Zealand bars. Our results clearly indicate exposure to SHS, with regional and seasonal variation, prior to the introduction of smokefree legislation.