SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Earthquake

249

In Fukushima, Japan, a prolonged refugee situation caused by a major nuclear incident after the earthquake of March 11, 2011 has led to the unintentional abandonment of many pets. We received stray or abandoned dogs from rescue centers in Fukushima Prefecture. During re-socialization training and health care, we accessed the behavioral characteristics and the urine cortisol level of each dog and compared them with those of other abandoned dogs not involved in this earthquake. The dogs from Fukushima showed significantly lower aggression toward unfamiliar people, trainability, and attachment to their caretakers; also, urine cortisol levels in the dogs from Fukushima were 5-10-fold higher than those in abandoned dogs from another area of Japan. These results suggested that the dogs from Fukushima suffered through an extremely stressful crisis.

Concepts: Health care, Japan, Dog, Earthquake, Prefectures of Japan, Fukushima Prefecture, Tōhoku region, Honshū

165

The evolution of shear rupture fronts in laboratory earthquakes is analysed with the corresponding functional networks, constructed over acoustic emission friction-patterns. We show that the mesoscopic characteristics of functional networks carry the characteristic time for each phase of the rupture evolution. The classified rupture fronts in network states-obtained from a saw-cut fault and natural faulted Westerly granite - show a clear separation into three main groups, indicating different states of rupture fronts. With respect to the scaling of local ruptures' durations with the networks' parameters, we show that the gap in the classified fronts could be related to the possibility of a separation between slow and regular fronts.

Concepts: 1980s music groups, Earthquake, Fault, Shear, Structural geology

154

Abnormal increases in radon ((222)Rn, half-life = 3.82 days) activity have occasionally been observed in underground environments before major earthquakes. However, (222)Rn alone could not be used to forecast earthquakes since it can also be increased due to diffusive inputs over its lifetime. Here, we show that a very short-lived isotope, thoron ((220)Rn, half-life = 55.6 s; mean life = 80 s), in a cave can record earthquake signals without interference from other environmental effects. We monitored (220)Rn together with (222)Rn in air of a limestone-cave in Korea for one year. Unusually large (220)Rn peaks were observed only in February 2011, preceding the 2011 M9.0 Tohoku-Oki Earthquake, Japan, while large (222)Rn peaks were observed in both February 2011 and the summer. Based on our analyses, we suggest that the anomalous peaks of (222)Rn and (220)Rn activities observed in February were precursory signals related to the Tohoku-Oki Earthquake. Thus, the (220)Rn-(222)Rn combined isotope pair method can present new opportunities for earthquake forecasting if the technique is extensively employed in earthquake monitoring networks around the world.

Concepts: Future, Japan, Forecasting, Earthquake, Earthquake prediction, Aftershock, 1906 San Francisco earthquake, Earthquakes

104

To assess whether recent seismicity is induced by human activity or is of natural origin, we analyze fault displacements on high-resolution seismic reflection profiles for two regions in the central United States (CUS): the Fort Worth Basin (FWB) of Texas and the northern Mississippi embayment (NME). Since 2009, earthquake activity in the CUS has increased markedly, and numerous publications suggest that this increase is primarily due to induced earthquakes caused by deep-well injection of wastewater, both flowback water from hydrofracturing operations and produced water accompanying hydrocarbon production. Alternatively, some argue that these earthquakes are natural and that the seismicity increase is a normal variation that occurs over millions of years. Our analysis shows that within the NME, faults deform both Quaternary alluvium and underlying sediments dating from Paleozoic through Tertiary, with displacement increasing with geologic unit age, documenting a long history of natural activity. In the FWB, a region of ongoing wastewater injection, basement faults show deformation of the Proterozoic and Paleozoic units, but little or no deformation of younger strata. Specifically, vertical displacements in the post-Pennsylvanian formations, if any, are below the resolution (~15 m) of the seismic data, far less than expected had these faults accumulated deformation over millions of years. Our results support the assertion that recent FWB earthquakes are of induced origin; this conclusion is entirely independent of analyses correlating seismicity and wastewater injection practices. To our knowledge, this is the first study to discriminate natural and induced seismicity using classical structural geology analysis techniques.

Concepts: Geology, Earthquake, Earthquake engineering, Seismic wave, Seismology, Fault, Reflection seismology, Seismometer

81

The next major earthquake to strike the ~7 million residents of the San Francisco Bay Area will most likely result from rupture of the Hayward or Rodgers Creek faults. Until now, the relationship between these two faults beneath San Pablo Bay has been a mystery. Detailed subsurface imaging provides definitive evidence of active faulting along the Hayward fault as it traverses San Pablo Bay and bends ~10° to the right toward the Rodgers Creek fault. Integrated geophysical interpretation and kinematic modeling show that the Hayward and Rodgers Creek faults are directly connected at the surface-a geometric relationship that has significant implications for earthquake dynamics and seismic hazard. A direct link enables simultaneous rupture of the Hayward and Rodgers Creek faults, a scenario that could result in a major earthquake (M = 7.4) that would cause extensive damage and loss of life with global economic impact.

Concepts: Earthquake, San Francisco Bay Area, San Francisco Bay, San Jose, California, San Andreas Fault, Richmond, California, Contra Costa County, California, San Francisco – Oakland Bay Bridge

72

Serpentinization-fueled systems in the cool, hydrated forearc mantle of subduction zones may provide an environment that supports deep chemolithoautotrophic life. Here, we examine serpentinite clasts expelled from mud volcanoes above the Izu-Bonin-Mariana subduction zone forearc (Pacific Ocean) that contain complex organic matter and nanosized Ni-Fe alloys. Using time-of-flight secondary ion mass spectrometry and Raman spectroscopy, we determined that the organic matter consists of a mixture of aliphatic and aromatic compounds and functional groups such as amides. Although an abiotic or subduction slab-derived fluid origin cannot be excluded, the similarities between the molecular signatures identified in the clasts and those of bacteria-derived biopolymers from other serpentinizing systems hint at the possibility of deep microbial life within the forearc. To test this hypothesis, we coupled the currently known temperature limit for life, 122 °C, with a heat conduction model that predicts a potential depth limit for life within the forearc at ∼10,000 m below the seafloor. This is deeper than the 122 °C isotherm in known oceanic serpentinizing regions and an order of magnitude deeper than the downhole temperature at the serpentinized Atlantis Massif oceanic core complex, Mid-Atlantic Ridge. We suggest that the organic-rich serpentinites may be indicators for microbial life deep within or below the mud volcano. Thus, the hydrated forearc mantle may represent one of Earth’s largest hidden microbial ecosystems. These types of protected ecosystems may have allowed the deep biosphere to thrive, despite violent phases during Earth’s history such as the late heavy bombardment and global mass extinctions.

Concepts: Spectroscopy, Earth, Plate tectonics, Geology, Earthquake, Volcano, Crust, Convergent boundary

71

Paleoenvironmental records from a southern California coastal saltmarsh reveal evidence for repeated late Holocene coseismic subsidence events. Field analysis of sediment gouge cores established discrete lithostratigraphic units extend across the wetland. Detailed sediment analyses reveal abrupt changes in lithology, percent total organic matter, grain size, and magnetic susceptibility. Microfossil analyses indicate that predominantly freshwater deposits bury relic intertidal deposits at three distinct depths. Radiocarbon dating indicates that the three burial events occurred in the last 2000 calendar years. Two of the three events are contemporaneous with large-magnitude paleoearthquakes along the Newport-Inglewood/Rose Canyon fault system. From these data, we infer that during large magnitude earthquakes a step-over along the fault zone results in the vertical displacement of an approximately 5-km(2) area that is consistent with the footprint of an estuary identified in pre-development maps. These findings provide insight on the evolution of the saltmarsh, coseismic deformation and earthquake recurrence in a wide area of southern California, and sensitive habitat already threatened by eustatic sea level rise.

Concepts: Water, Sea level, Oceanography, Geology, Earthquake, Organic matter, Cartography, Fault

66

Transient gravity changes are expected to occur at all distances during an earthquake rupture, even before the arrival of seismic waves. Here we report on the search of such a prompt gravity signal in data recorded by a superconducting gravimeter and broadband seismometers during the 2011 Mw 9.0 Tohoku-Oki earthquake. During the earthquake rupture, a signal exceeding the background noise is observed with a statistical significance higher than 99% and an amplitude of a fraction of μGal, consistent in sign and order of magnitude with theoretical predictions from a first-order model. While prompt gravity signal detection with state-of-the-art gravimeters and seismometers is challenged by background seismic noise, its robust detection with gravity gradiometers under development could open new directions in earthquake seismology, and overcome fundamental limitations of current earthquake early-warning systems imposed by the propagation speed of seismic waves.

Concepts: Scientific method, Wave, Earthquake, Seismic wave, Seismology, Geophysics, Seismometer, Love wave

56

On 22 February 2011, Christchurch New Zealand (population 367,700) experienced a devastating earthquake, causing extensive damage and killing one hundred and eighty-five people. The earthquake and aftershocks occurred between the 2009 and 2011 waves of a longitudinal probability sample conducted in New Zealand, enabling us to examine how a natural disaster of this magnitude affected deeply held commitments and global ratings of personal health, depending on earthquake exposure. We first investigated whether the earthquake-affected were more likely to believe in God. Consistent with the Religious Comfort Hypothesis, religious faith increased among the earthquake-affected, despite an overall decline in religious faith elsewhere. This result offers the first population-level demonstration that secular people turn to religion at times of natural crisis. We then examined whether religious affiliation was associated with differences in subjective ratings of personal health. We found no evidence for superior buffering from having religious faith. Among those affected by the earthquake, however, a loss of faith was associated with significant subjective health declines. Those who lost faith elsewhere in the country did not experience similar health declines. Our findings suggest that religious conversion after a natural disaster is unlikely to improve subjective well-being, yet upholding faith might be an important step on the road to recovery.

Concepts: Causality, Belief, Faith, Philosophy, New Zealand, Religion, Earthquake, God

54

Earthquakes in unusual locations have become an important topic of discussion in both North America and Europe, owing to the concern that industrial activity could cause damaging earthquakes. It has long been understood that earthquakes can be induced by impoundment of reservoirs, surface and underground mining, withdrawal of fluids and gas from the subsurface, and injection of fluids into underground formations. Injection-induced earthquakes have, in particular, become a focus of discussion as the application of hydraulic fracturing to tight shale formations is enabling the production of oil and gas from previously unproductive formations. Earthquakes can be induced as part of the process to stimulate the production from tight shale formations, or by disposal of wastewater associated with stimulation and production. Here, I review recent seismic activity that may be associated with industrial activity, with a focus on the disposal of wastewater by injection in deep wells; assess the scientific understanding of induced earthquakes; and discuss the key scientific challenges to be met for assessing this hazard.

Concepts: Perception, Europe, Liquid, Earthquake, Dam, Earthquake engineering, Seismic wave, Seismology