New Research Opportunities in the Earth Sciences - New Research Opportunities in the Earth Sciences - page 30

submicrometer-sized, datable zircons and oxide exsolution structures from the early Archean
period is needed.
There are two essential requirements for such progress, and both can be within
reach if collaborative and focused efforts are now initiated on two fronts. One is the
development of novel SQUID and non-SQUID sensors (e.g., spin-exchange relaxation free or
Spin Exchange Relaxation-Free [SERF] method-based) that are capable of measuring
submillimeter samples, and signal enhancement techniques for the very small magnetic
signals that such scanning techniques will deliver. The second requirement is inherently
linked to the first and involves “ground truthing” magnetic measurements that are based on
submillimeter samples. Because these samples are single crystals, there are a number of
rock magnetic effects that must be examined in order to ensure that they are accurate
recorders of Earth's magnetic field. These effects include remanence anisotropy due to
crystallographic alignment of magnetic oxides within the silicate host, magnetostatic
interactions between inclusions, and subsolidus exsolution structures within the oxides.
Measuring the importance of these effects will require the use of instruments capable of
imaging magnetism at scales of 10 to 1,000 nm, such as transmission electron microscopes
and magnetic force microscopes. Ultimately these kinds of studies will allow researchers to
select only those samples that can be confidently used for reconstruction of geomagnetic
paleointensity for such ancient times.
FAULTING AND DEFORMATION PROCESSES
Plate tectonics provides a first-order description of how Earth's surface shifts
with time, with the motions near plate boundaries largely involving seismic or
aseismic faulting and elastic or anelastic rock deformation. Plate motions driven by
mantle flow concentrate stresses on faults at plate boundaries, powering the cycle of
frictional stress accumulation, elastic and anelastic strain deformation, and slow or
abrupt (earthquake) fault displacement and stress and strain release. Ground motions
caused by elastic waves and surface deformations produced during rapid earthquake
faulting constitute one of nature's greatest hazards, with tremendous annual loss of
life and damage on a global basis. The impact of earthquakes can be staggering;
hundreds of thousands of fatalities in moderate-size events like the 2010 Haiti
(magnitude M w 7.0) earthquake or immense events like the 2004 Sumatra (M w 9.2)
earthquake and tsunami, and hundreds of billions of dollars in damage as in the 2011
Japan (M w 9.0) earthquake. Since 2004 there have been more great earthquakes
around the world than in any 6.5-year period in seismological history (back to 1900),
and burgeoning population growth near plate boundaries will place ever-increasing
populations and built infrastructure at risk throughout this century. Efforts to
understand how faults accumulate and release stress and strain and the nature of the
resulting ground motions constitute major scientific challenges highlighted in
community planning documents from seismologists (Lay, 2009), geodesists
(UNAVCO, 2008), geodynamicists (Olson, 2010), GEOPrisms (MARGINS Office,
2010), and the EarthScope program (Williams et al., 2010). The 2008 NRC report
Origin and Evolution of Earth highlighted the question of whether earthquakes,
volcanic eruptions, and their consequences can be predicted, as one of 10 Grand
Challenges in the Earth sciences.
Earthquake science is intrinsically interdisciplinary and deals with complex
multiscale dynamical systems spanning the microscale processes of friction and fluids
in fault zones to the macroscale processes of elastic and anelastic crustal deformations