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orniawere devising a way to make parisons between one earthquake and the next。 they werecharles richter and beno gutenberg； though for reasons that have nothing to do with fairnessthe scale became known almost at once as richter’s alone。 （it has nothing to do with richtereither。 a modest fellow； he never referred to the scale by his own name； but always called it“the magnitude scale。”）the richter scale has always been widely misunderstood by nonscientists； though perhapsa little less so now than in its early days when visitors to richter’s office often asked to seehis celebrated scale； thinking it was some kind of machine。 the scale is of course more anidea than an object； an arbitrary measure of the earth’s tremblings based on surfacemeasurements。 it rises exponentially； so that a 7。3 quake is fifty times more powerful than a6。3 earthquake and 2；500 times more powerful than a 5。3 earthquake。
at least theoretically； there is no upper limit for an earthquake—nor； e to that； a lowerlimit。 the scale is a simple measure of force； but says nothing about damage。 a magnitude 7quake happening deep in the mantle—say； four hundred miles down—might cause no surfacedamage at all； while a significantly smaller one happening just four miles under the surfacecould wreak widespread devastation。 much； too； depends on the nature of the subsoil； thequake’s duration； the frequency and severity of aftershocks； and the physical setting of theaffected area。 all this means that the most fearsome quakes are not necessarily the mostforceful； though force obviously counts for a lot。
the largest earthquake since the scale’s invention was （depending on which source youcredit） either one centered on prince william sound in alaska in march 1964； whichmeasured 9。2 on the richter scale； or one in the pacific ocean off the coast of chile in 1960；which was initially logged at 8。6 magnitude but later revised upward by some authorities（including the united states geological survey） to a truly grand…scale 9。5。 as you will gatherfrom this； measuring earthquakes is not always an exact science； particularly wheninterpreting readings from remote locations。 at all events； both quakes were whopping。 the1960 quake not only caused widespread damage across coastal south america； but also set offa giant tsunami that rolled six thousand miles across the pacific and slapped away much ofdowntown hilo； hawaii； destroying five hundred buildings and killing sixty people。 similarwave surges claimed yet more victims as far away as japan and the philippines。
for pure； focused； devastation； however； probably the most intense earthquake in recordedhistory was one that struck—and essentially shook to pieces—lisbon； portugal； on all saintsday （november 1）； 1755。 just before ten in the morning； the city was hit by a suddensideways lurch now estimated at magnitude 9。0 and shaken ferociously for seven full minutes。
the convulsive force was so great that the water rushed out of the city’s harbor and returnedin a wave fifty feet high； adding to the destruction。 when at last the motion ceased； survivorsenjoyed just three minutes of calm before a second shock came； only slightly less severe thanthe first。 a third and final shock followed two hours later。 at the end of it all； sixty thousandpeople were dead and virtually every building for miles reduced to rubble。 the san franciscoearthquake of 1906； for parison； measured an estimated 7。8 on the richter scale andlasted less than thirty seconds。
earthquakes are fairly mon。 every day on average somewhere in the world there aretwo of magnitude 2。0 or greater—that’s enough to give anyone nearby a pretty good jolt。
although they tend to cluster in certain places—notably around the rim of the pacific—theycan occur almost anywhere。 in the united states； only florida； eastern texas； and the uppermidwest seem—so far—to be almost entirely immune。 new england has had two quakes ofmagnitude 6。0 or greater in the last two hundred years。 in april 2002； the region experienceda 5。1 magnitude shaking in a quake near lake champlain on the new york–vermont border；causing extensive local damage and （i can attest） knocking pictures from walls and childrenfrom beds as far away as new hampshire。
the most mon types of earthquakes are those where two plates meet； as in californiaalong the san andreas fault。 as the plates push against each other； pressures build up untilone or the other gives way。 in general； the longer the interval between quakes； the greater thepent…up pressure and thus the greater the scope for a really big jolt。 this is a particular worryfor tokyo； which bill mcguire； a hazards specialist at university college london； describesas “the city waiting to die” （not a motto you will find on many tourism leaflets）。 tokyo standson the boundary of three tectonic plates in a country already well known for its seismicinstability。 in 1995； as you will remember； the city of kobe； three hundred miles to the west；was struck by a magnitude 7。2 quake； which killed 6；394 people。 the damage was estimatedat 99 billion。 but that was as nothing—well； as paratively little—pared with whatmay await tokyo。
tokyo has already suffered one of the most devastating earthquakes in modern times。 onseptember 1； 1923； just before noon； the city was hit by what is known as the great kantoquake—an event more than ten times more powerful than kobe’s earthquake。 two hundredthousand people were killed。 since that time； tokyo has been eerily quiet； so the strainbeneath the surface has been building for eighty years。 eventually it is bound to snap。 in 1923；tokyo had a population of about three million。 today it is approaching thirty million。 nobodycares to guess how many people might die； but the potential economic cost has been put ashigh as 7 trillion。
even more unnerving； because they are less well understood and capable of occurringanywhere at any time； are the rarer type of shakings known as intraplate quakes。 thesehappen away from plate boundaries； which makes them wholly unpredictable。 and becausethey e from a much greater depth； they tend to propagate over much wider areas。 themost notorious such quakes ever to hit the united states were a series of three in newmadrid； missouri； in the winter of 1811–12。 the adventure started just after midnight on december 16 when people were awakened first by the noise of panicking farm animals （therestiveness of animals before quakes is not an old wives’ tale； but is in fact well established；though not at all understood） and then by an almighty rupturing noise from deep within theearth。 emerging from their houses； locals found the land rolling in waves up to three feet highand opening up in fissures several feet deep。 a strong smell of sulfur filled the air。 theshaking lasted for four minutes with the usual devastating effects to property。 among thewitnesses was the artist john james audubon； who happened to be in the area。 the quakeradiated outward with such force that it knocked down chimneys in cincinnati four hundredmiles away and； according to at least one account； “wrecked boats in east coast harbors and 。
。 。 even collapsed scaffolding erected around the capitol building in washingto