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Earth, a living planet under surveillance

By Vincent Defait, translated by Summer Mercier

Translated Monday 23 January 2006, by Summer

Environment. Earthquakes, floods, and hurricanes... These are the extreme natural phenomena that scientists are monitoring at all possible latitudes. Journey across and beneath the surface of a planet living under close scrutiny.

The Earth split open for eight long minutes. The seabed displaced an enormous mass of water as it rose by approximately fifteen meters along the entire length of a one thousand kilometer fault. The wall of water sped along at 800 km/h. A few minutes, a few hours later, the sea invaded the land, killing and destroying. On December 26th, 2004, no one saw anything coming. Earth sent man a reminder: It’s alive.

The lack of preparedness was not for lack of watchfulness. From one end of the globe to the other, from the depths of the oceans to the heights of space, scientists have their eyes riveted on Earth in quasi permanence. Seismometers, marigrams, satellites and other instruments scan the planet, but for all of their information, can scientists really predict these catastrophes? In many scientific domains, the exercise is risky.

The globe burns, shifts, and lets off gas. Its core boils, intermittently spitting lava onto the surface. High speed winds rage over land and water, creating depressions and anticyclones. Throughout the atmosphere, gases interchange, merge, and either protect or damage the Earth. This is a permanent dynamic. Quakes kill, hurricanes raze, greenhouse gases spark extreme heat. Paradoxically, without this geophysics and chemistry, life would be stifled. Earth, a living planet, plays games with those who might otherwise like to take control.

From the center to the surface of the globe, elevated pressures and temperatures blend matter, creating a more or less liquid core and a very solid, thick crust. In this way, Earth’s rocks are continually regenerated. “We know the first seven hundred kilometers very well,” explains Geneviève Roult, head of Geoscope, a network of thirty French recording stations in both hemispheres, since 1982. The depths of the globe and the boundaries between different layers remain a mystery. “The Earth’s crust is not homogeneous,” we are reminded at the Center for atomic studies (CEA). A dozen plates, about one hundred kilometers thick, “float” on the surface of fused rock, or magma. These plates adjust by a few centimeters each year. Not much on the global scale, but enough so that as the millennia slip by, the continents separate. India, for example, was in the southern hemisphere 65 million years ago. The famous tectonic plates. From time to time, these plates rub together or collide violently. Each year, the surface of the globe shakes 130,000 times with magnitudes equal to at least 3. Gentle quakes, barely detectable by our senses. More stirring than these are the hundreds of quakes that achieve a magnitude of 6, and the rare quakes, more dangerous, which rise above a magnitude of 8.

According to Geneviève Roult, scientist use the Geoscope network to “continuously record the movement of the ground." Objective: to study the tectonic mechanisms and “scan” the Earth in order to understand its structure. “We’re learning little by little,” the scientist admits. The French network is not the only one taking the planet’s pulse. The United States have IRIS (Icorporated Research Institutions for Seismology). In addition, these smaller groups of seismologists come together to form an international federation.

Is this organization enough to anticipate seismic activity? No one knows. Earthquakes usually don’t warn before they strike. Based on three distinct time frames, forecasts are made despite uncertainties. First of all, in the long term, they are made by reconstructing the seismic history of a given region. Next, using a shorter time scale, they are made by studying the rhythm of the seismic activity. “That way, we know when we are a few years away from a rupture,” explains Pascal Bernard, seismologist at the Institute of Global Physics in Paris. Using this method, a recent study established, with a probability of 90%, that an important quake will shake Istanbul, the capital of Turkey, within the next three decades. The same prediction for San Francisco, in the United States, with firmer statistics. Last but not least, in the short term, scientists identify possible “precursory" signs. “Microseisms often occur a few hours or a few days before a quake,” explains Pascal Bernard. The problem: “These smaller episodes are often followed... by an absence of seismic activity.”

As technologies evolve, scientists take to the air and observe Earth’s geophysics and climate from space. Satellites are swarming in orbit, their noses pointed at the globe. From now until 2008, six Franco-American machines are destined to revolve at several minute-long intervals while focusing on the atmosphere. Invesat, Météosat and EarthCARE are a few of the European missions peering in on Earth’s climate. “With the satellites, we can measure the height of oceans within a millimeter of precision,” describes geophysicist José Achache. “We have thus learned that in ten years the level of the oceans has increased by an average of thirty millimeters. And that allows us to have a better understanding of the condition of the ocean, currents, and climactic phenomena.”

The ultimate goal of seismologists, geophysicists, and climatologists: the GEOSS, Global Earth Observation System of Systems, born out of an international agreement in Februarys 2005. Its embryo, the GEO (inter-governmental Group on Earth Observations), currently reunites 60 states and 43 international organizations. “It’s a system of information for the environment,” summarizes José Achache, once with the European space agency, and since September 2005 at the head of GEO. At the end of the 1990s, the scientist was already active in GMES, the European program supporting “global monitoring for environment and security.” The GMES plans to integrate the future “system of systems” and acheive, in short, a global surveillance of global phenomena.

Keeping an eye on the planet’s humors is not enough. Compared to seismic activity, which is still difficult to predict, the consequences of climactic change and other perturbations, like floods or droughts, can easily be anticipated. Is it necessary to follow through on every scientist’s warning? If this were the case, how could the public powers-that-be prepare themselves for the consequences? “There’s not much else to do but to educate people,” José Achache declares. “We should show authorities what observation and prevention are capable of, to prove their reliability, and brainstorm with them to find the best way to take the information into account.”

Vincent Defait

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