Low Coseismic Friction on the Tohoku-Oki Fault Determined from Temperature Measurements

The frictional resistance on a fault during slip controls earthquake dynamics. Friction dissipates heat during an earthquake; therefore the fault temperature after an earthquake provides insight into the level of friction. The JFAST project (IODP Expedition 343/343T) installed a borehole temperature observatory 16 months after the March 2011 M[subscript w]9.0 Tohoku-Oki earthquake across the fault where slip was ~50 m near the trench. After 9 months of operation, the complete sensor string was recovered. A 0.31°C temperature anomaly at the plate boundary fault corresponds to 27 MJ/m² of dissipated energy during the earthquake. The resulting apparent friction coefficient of 0.08 is considerably smaller than static values for most rocks.This is the author’s version of the work. It is posted here by permission of the AAAS for personal use, not for redistribution. The definitive version was published in Science, Volume 342 issue 6163 on 06 December 2013, DOI:10.1126/science.1243641

Low Coseismic Friction on the Tohoku-Oki Fault Determined from Temperature Measurements

The frictional resistance on a fault during slip controls earthquake dynamics. Friction dissipates heat during an earthquake; therefore, the fault temperature after an earthquake provides insight into the level of friction. The Japan Trench Fast Drilling Project (Integrated Ocean Drilling Program Expedition 343 and 343T) installed a borehole temperature observatory 16 months after the March 2011 moment magnitude 9.0 Tohoku-Oki earthquake across the fault where slip was ~50 meters near the trench. After 9 months of operation, the complete sensor string was recovered. A 0.31°C temperature anomaly at the plate boundary fault corresponds to 27 megajoules per square meter of dissipated energy during the earthquake. The resulting apparent friction coefficient of 0.08 is considerably smaller than static values for most rocks

EFFECT OF AGE ON FIREFIGHTER FITNESS IN A DEPARTMENT WITH ANNUAL FITNESS ASSESSMENTS

Arasta Wahab1, Mike Toczko1, Robert Lockie2, Shane Caswell1, Joel Martin1. 1George Mason University, Manassas, VA. 2California State University, Fullerton, CA. BACKGROUND: The firefighter (FF) profession is demanding job that includes high-intensity physical work. As a result, maintaining appropriate levels of fitness are encouraged for FFs to perform occupational duties, prevent health issues and musculoskeletal injuries. The purpose of the present study was to examine the effect of age on fitness in a large cohort of professional FFs required to complete an annual fitness assessment. METHODS: Retrospective fitness assessment and body composition data was obtained from 1076 professional FFs (males=955, females=121) who completed an annual fitness assessment. The fitness assessment included maximum pull-ups, maximum push-ups, maximum curl-ups, and a 3-minute step test to estimate aerobic fitness. Fat mass percentage (FM%) was assessed using bioelectric impedance analysis. Participants were categorized into 4 age groups (20-29, 30-39, 40-49, 50-59 years). Analyses of variance and Tukey’s Post-hoc test were used to assess the effect of age on fitness measures. All statistics were conducted with R software and a significance level of p=0.05. RESULTS: A total of 170 (15.8%), 332 (30.9%), 357 (33.2%) and 217 (20.2%) FFs were in the 20-29, 30-39, 40-49, 50-59 age groups, respectively. There was a significant difference between age groups for pull-ups (F(3,1072)=52.11, p\u3c0.001, η2=0.13), curl-ups F(3,1072)=57.56, p \u3c0.001, η2=0.14), push-ups (F(3,1072)=50.74, p\u3c0.001, η2=0.12) and FM% F(3,1072)=22.82, p\u3c0.001, η2=0.06). Post-hoc testing revealed that pull-ups, curl-ups and push-ups significantly (p\u3c0.05) declined each decade except when comparing the 20-29 to 30-39 age groups. FM% was significantly worse (p\u3c0.05) each decade except for the 40-49 compared to 50-59 year age group. There was no significant main effect for age on aerobic capacity (F(3,1072)=0.55, p=0.649, η2=0.001). CONCLUSION: The current findings indicate that muscular fitness and FM% generally declined with age while aerobic fitness was preserved in professional FF. Muscular fitness did not decline until FF were older than 40 years, while FM% increased in younger age groups then was unchanged after the age of 40. Fire departments implementing health and fitness programs could consider tailoring programs to prevent increases in FM% in younger FFs (\u3c40 years) and maintaining muscular fitness in older FFs (\u3e40 years)

EFFECTS OF IMPLEMENTING A CONSEQUENTIAL ANNUAL FITNESS ASSESSMENT IN A LARGE COUNTY FIRE DEPARTMENT

Michael Toczko1, Robert Lockie2, Megan Sax van der Weyden1, Marcie Fyock-Martin1, Joel Martin1. 1George Mason University, Manassas, VA. 2California State University, Fullerton, CA. INTRODUCTION: To become a firefighter (FF) individuals must pass physically demanding exams, which assess ability to perform job tasks prior to entering a training academy. Despite the importance of health and fitness for FF only about 30% of US fire departments have health and wellness programs. Recently, a fire department in the US implemented mandatory annual fitness testing with punitive consequences for substandard performance. The purpose of the study is to report the effects of implementing a consequential fitness assessment (FA) within a fire department. METHODS: Retrospective data was provided from 1364 professional FF (Males:88%, Females: 12%, age: 40.0±8.8 yrs, years of service: 11.9±6.8 yrs) from 2019, 2020 and 2021. The FA consisted of maximum pull-ups (PL), maximum curl-ups (CU) within 60 seconds, maximum push-ups (PS) within 60 seconds, and 3-minute step test (ST) to estimate peak oxygen consumption. To examine the effect of exam year (EY) on fitness outcomes (FO) analyses of covariance (ANCOVA) were conducted while controlling for age and sex. Tukey’s Post-hoc Test were used to determine any significance differences between exam year (p\u3c0.05). RESULTS: The sample size for 2019, 2020, and 2021 were 1013, 777, and 1084 , respectively. There were no significant differences between sex distribution and age by EY. The ANCOVA revealed there was a significant small effect of EY on FO (PL: F(2, 2848) = 5.92, p \u3c0.01, η2= 0.003; CU: F(2, 2848) = 17.57, p \u3c0.001, η2= 0.01; PS: (F(2, 2848) = 18.50, p \u3c0.001, η2= 0.01; ST: F(2, 2848) = 26.19, p \u3c0.001, η2= 0.02). FF performance in 2021 was significantly better on CU, PS, and ST compared to 2019 (p\u3c0.001). PL performance in 2021 was significantly better than 2020 (p\u3c0.01). FF performed significantly better on CU and ST in 2020 than 2019 (p\u3c0.01). CONCLUSION: The results suggest the implementation of a consequential FA may be a plausible method for FF to maintain sufficient fitness to meet occupational demands. Although there was a significant difference between FO by EY it is not evident whether the small FO changes lead to increased performance of occupational tasks. Future research should explore whether changes in fitness lead to improvements in ability to perform occupational tasks

5.3 year time series of formation pore fluid pressure and temperature from IODP Hole 319-C0010A measured by GeniusPlug from 2010 to 2016

One primary objective of Integrated Ocean Drilling Program Expedition 365, conducted as part of the Nankai Trough Seismogenic Zone Experiment, was to recover a temporary observatory emplaced to monitor formation pore fluid pressure and temperature within a splay fault in the Nankai subduction zone offshore SW Honshu, Japan. Here we use a 5.3 year time series of formation pore fluid pressure, and in particular the response to ocean tidal loading, to evaluate changes in pore pressure and formation and fluid elastic properties induced by earthquakes. Our analysis reveals 31 earthquake‐induced perturbations. These are dominantly characterized by small transient increases in pressure (28 events) and decreases in ocean tidal loading efficiency (14 events) that reflect changes to formation or fluid compressibility. The observed perturbations follow a magnitude‐distance threshold similar to that reported for earthquake‐driven hydrological effects in other settings. To explore the mechanisms that cause these changes, we evaluate the expected static and dynamic strains from each earthquake. The expected static strains are too small to explain the observed pressure changes. In contrast, estimated dynamic strains correlate with the magnitude of changes in both pressure and loading efficiency. We propose potential mechanism for the changes and subsequent recovery, which is exsolution of dissolved gas in interstitial fluids in response to shaking