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by: Jeremy Steuber


Jeremy Steuber

GPA 3.87

William Travis

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William Travis
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This 113 page Class Notes was uploaded by Jeremy Steuber on Thursday October 29, 2015. The Class Notes belongs to GEOG 3402 at University of Colorado at Boulder taught by William Travis in Fall. Since its upload, it has received 28 views. For similar materials see /class/231899/geog-3402-university-of-colorado-at-boulder in Geography at University of Colorado at Boulder.




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Date Created: 10/29/15
Reminder Main Principles Hazards from interaction of human and physical systems Exposure and vulnerability Risk likelihood X consequence p r Risk reduction hazard adjustment Modify the event spread the loss reduce societal vulnerability Cost vs benefit Reminder Main Principles Risk assessment Physical protection Relief recovery insurance Forecast and warning systems Building design and engineering Land use Chap 6 Volcanoes 500 active 50 erupt year Not big source of fatalities yet still 1000 year Not big property damage because most in rural areas OK not true for Rainer and Etna Or Hawaiian but those are different not explosive Potential for catastrophic eruptions from explosive volcanoes aka composite or even strato volcanoes Hazard zone occupation increasing esp So America and Se Asia Indonesia esp Some volcanoes are monitored by web cam httpwwwavoalaskaedu httpwwwfsfedusqpnfvolcanocamsmsh Volcanoes Three geographic types Subduction 80 and more explosive Rift Iceland effusive and Hot Spot Hawaii effusive Yellowstone explosive There is rather poor frequencymagnitude data globally and for individual volcanoes so p r and risk are difficult to quantify No real comparative measures of magnitude of eruptions though volume of lava and ash is now used Newhall and Self s VEI Table 61 Lava type felsic vs mafic structure Plinean vs Pelean etc Eruption Coiurnn Landslide Debris Avalancha I quothr lquotquot lul Iv I 3quot k 55 WWW fE5 39 Prevailing 39 3939 cid R39a39i 39 Wind Pyroclusllc How quot1 quotI V 39JVIquot 139 I Bombs f n V 39 quotI WI 3 Low Dome quotI lquot y39vHQ i39IJ39H Dome Collapse w H F ymclus c Haw Funlambs Ma mu Reservoir Figure 6 I SECUOD through a compnsite mlumic mac showing a wide range of possible hazards Same hazards pyrmlasric and law aws OCCUI39 during cruptinns cht f hazards Inhars may occur after the event Tamra after Main a at 2001 Volcanic Hazards Pyroclastic flows most deaths nuees ardentes Mt Pelee 1902 St Pierre Ashfall tephra 1 km3 plus Lava flows Volcanic gases CO flows and collects in low spots Cameroon events Ground deformation Lahars mud flows Hazards Landslides on the slopes Tsunami with explosions and slope failure Volcn nk Hazards 000 10000 Distance km Fizm 62 The in ucnuc nidnnuwe on dcurmnvs vnlmnn phrnomcrm Mum hazards are mama m a 1n km Wm 10 V lmno bur hu c ecm or39h m uh gases and mmumi Waves can L xtund beyonr 10mm km Same AfterChesrer m 12ml Rspnmu I39mm Fm n mmmm H111N zl 1 mum um 39Hk ufums m h EffECIS uv39vnumm empnmu mpynght AZUUI mh pcmussum from Elsemr a Humming expnmrc Lava flows slow and fast Aerial view of Colima Volcano moments after a lava flow on the upper flank of the volcano collapsed the photograph is tilted slightly horizon is in upper right nuees ardente Mt Pelee Lahars on snowglacier clad volcanoes Lake Nyos Cameroon source of dangerous CO and 002 The Cascade allLBIkef umn pr peak A Mt Ste Helens classic strawvolcano Spring 1980 May 18 1980 Slope failure and lateral eruption this made area affected by blast larger than expected in the northern azimuths see later map Blast zone devastated note raft of logs in Spirit Lake Blast zone some ofvmich was occupied by timber cutters during emption A wet Timber 39 39 39 39 quot 39 USGS top assess risk quot 5 zone Ash plime visible on satellite images was a signi cant downwind hazard from Mt Ste Helens us we cKaJlsDell untann Mlssauln n oomem WASHINGTON 1 mm u n l Richland La 0 Mann 7 l in Y5 vaw vs OREGON y f l VF l w y 3 19m Imam mos repment mum d m this volume Lnk Lenny l gure qsu Isapal map 17 ash rmpled fmm Mount 5 Helms on M 39 quot quot quot 39 Iu nln n and Warden Lnkx me c1059 to Muses Luke and an nu shamquot separately Even 35 cm of ash causes transportation disruptions problems with water resources crops and human health mental and physical J4 7 Ashfall is an extensive hazard from volcanoes Ste Helens ash was widely distributed Mud ows caused by melting snow and glacier ice created extensive damage on tributaries coming off of Ste Helens several miles downstream A climb of St Helens ve years later Survey site to measure ground deforma ion Edge of the crater strata layers from previous eruptions barely visible Lava Dome in foreground blast area in mid ground Mt Rainer in background The US Army Corps of Engineers building as sediment retention structure on the Toutle River to catch extensive blast areagreater sediment will come down thru the systems for decades The Toutle dumps into the Columbia thus posing a problem for navigation Preeruption hazard map laid out mostly concentric risk areas plus linear flood zones New surface deposits map of Ste Helens indicates future risks and shows most pyroolastic deposition Orange spread out to the north by the lateral blast Ash and mudflow I lahar layers along Toutle River going back several thousand historic activity in areas now settled Careful monitoring of Sesimicity Ground deformation Thermal changes Geochemical changes May give some clues to coming eruptions but forecasting is difficult n g gi yz gquot quotf GEOWARN nmEummmma in ucod uph mm m m m mwly Early warning system wammzmm3917z uzquotquotquot quot quotquot m M m a m m gyman V 5mm quot1 m I 2 lmplemenlationto mm Es ima im f ac ty index 2mm sunw rum mnwdmkun my cum minalumni V Elknumuldwmmdwm mlun m XunurwnumsiLD ms vacuum Tm m MM WWWM w 2quot wlmln MIquot Wellnw Cummmwm w 33m Rating of correlations MERE 2212232 339 mwam mfn 1a7imhwnm mmquot M M Conealion analysis rm mix W 75 quot wzrrniass m ik 4113 wmmmmmm a mu m Rllk mmmm analysl m Immudini vlsk emu determin I identification of volcanic precu rsors r39 whichis 39 39 on a vol 39 Ahnl have extensive monitoring to allow some waming Hazard Reduction Challenges Monitoring Forecast and Warning still uncertain casebycase slowly developing technology and skill httpwwwfsfedusqpnfvolcanocamsmsh Freqmagnitude and risk analysis difficult because eruptions are rare geological data getting better see slide of Cascade eruption history Hazard zone determinationmapping getting easier with geological mapping of past deposits from pyroclastic flows and lahars Land use planning same as other hazards difficult to gte people to change land use for unlikely event Most volcano hazard zones gaining population Tuesday March 14 2006 1000 am PST 1800 UTC MOUNT ST HELENS UPDATE Current status is Volcano Advisory Alert Level 2 aviation color code ORANGE Growth of the new lava dome inside the crater of Mount St Helens continues accompanied by low rates of seismicity low emissions of steam and volcanic gases and minor production of ash During such eruptions changes in the level of activity can occur over days to months The eruption could intensify suddenly or with little warning and produce explosions that cause hazardous conditions within several miles of the crater and farther downwind Small ahars could suddenly descend the Toutle River iftriggered by heavy rain or by interaction of hot rocks with snow and ice These ahars pose a negligible hazard below the Sediment Retention Structure SRS but could pose a hazard along the river channel upstream Potential ash hazards Wind forecasts from the National Oceanic and Atmospheric Administration NOAA coupled with eruption models show that any ash clouds that rise above the crater rim today would drift northnortheastward in the morning then shift to a more eastward trajectory in the afternoon Potential ash hazards to aviation Under current eruptive conditions small shortlived explosions may produce ash clouds that exceed 30000 feet in altitude Ash from such events can travel 100 miles or more downwind Recent observations The mountain is obscured by clouds this morning with unsettled weather today Our instruments show no significant change in patterns of seismicity or deformation Seismicity continues its ongoing procession of small earthquakes every several minutes punctuated by the occasional larger earthquake eg a larger event at 413 PST on Monday The actively dome continues to extrude to the west ontrend with recent motion Monitoring data are within the range of their typical recent values The US Geological Survey and the University ofWashington continue to monitor the situation closely and will issue additional updates and changes in alert level as warranted Example of Volcano Hazard Warning statement for Ste Helens two years agonote vague wording and great uncertainties EXPLAN n Ii l ATION m mcmm a m K I limouer MilEs s Hazard assessment around Mt Rainer Few people live in potential pyroclasticllavalblast zone gray 150000 people live on previous Rainier lahars downstream Lahars and floods can go way down local drainages so NowCasting warning system in place on Puyallup and Carbon rivers senses mudflows coming down the river and sends out an alarm this is then sent via reverse 911 to downstream homes Cascade Eruptions During the Last 4000 Years Mount Baker f Glacier Peak i Mount Rainier Pacific Ocean Years Ago W V 50m My U555 atrier ew1947585 The standard frequencymagnitude approach to assessing volcanic risk is problematic events are rare and clumped Still data getting better what cascade volcanoes would you worry about the most Ste Helens would have looked like a good bet for trouble had this record been available before 1980 and though Rainer shows less activity than some others it is not dormant and has higher risk due to population Shasta is also one to watch for same reason population and even major reservoirs nearby Droughts Chap 11 Creeping hazard slow onset longduration chronic large areal extent Worldwide not tied to certain geography though more frequent in semiarid climates Linked to Famine in complex ways Box 111 Caused by absence rather than presence of a geo physical phenomenon precipitation Magnitude Measured as Departure from normal percent or absolute values Drought index a combination of cumulative departures in rain hydrology soil moisture etc like the Palmer Drought Severity lndex PDSI Various lmpact measures Runoff lake levels reservoir storage soil moisture crop yields etc Historic events Great Plains Dust Bowl 19305 Sahelian Drought 1960519805 Slandaldimd JJASO nean Sahel rainfall 189872000 i M Mm Ema Ing FREQUENCY Franny Ran uuRATmN Lang sum AHEAL EXTENV wmmrem IIIDF WC Liuuxen 5pm or omsn Sh Fm 9ATIALDISPERSIUN mum Cmcamraud TEMPORALSPACING39 han aanuom FIGUHEZ4 HAZAFID EVENT PROFILES FOH CHARACTERISTIC DROUGHT BLIZZARD EARTHQUAKE 39 39 aprofieu r4 39 I make comparisons between evenls by chalaclerislwcs independent of their human impact Standardized HASH mean Sahel rainfall IEQB ZDIIJ IJ I I a t Standardized HAITI waned Ia EDS I 993 1390 1930 1D 1D 3D 4D 1950 6339 TD Drought in rthe African Sahel figures prominently in international annals of drought impacts and in text Box 112 Be sure to read that Its most remarkable feature was its raw persistence over decades which Smith attributes both to large scale forcing by remote atmospheric forces and regional feedbacks among precipitation soil moisture vegetation radiation balance and climate Cn oradn Smtewlde Precipilailnn camels Depamureadan 13993 Hm EDGE i J5 Two examples of drought measures of magnitude departures from normal in this case average for a whole state left and average g statewide Palmer drought index I mrwrvui 1 I mural f f I A 39 quoty l has dim minmm w 1 item ml Balsamdo amenile PHDI39 Jam 5 mammwm smssm Pamr rumba rmlyi Irma HAW Cm timi 139 55m J HOM u39nld 91m ElJ39I U S Drought Monitor W m mmwm Dmm g ha limping Typm A39w lj l Emma Llsz l 390 mum Em mwm wm W W413 My Ii alowal F I Fit rlJnnir fWBIdli 35 July 23 2002 53 WJW E 39l nelan an demmammu am lb Drww Erwp39llunll blurpi Al 3lmpm 39l 39 Th9 Drelag hr an l qr Juntaquot M bmaduwle rm1 Silica v Laud man39uiasu my very 5w accumpang uuz hm llllrllllll39f s o m furl Nit Martians mpIidmugmunmdumm mm mm mam Lisa A drought index like palmer can also be mapped spatially And is index can be mapped then area can be calculated Here is area in percent of Colorado in Severe or Worse ltPDSI 4 rought iCDLDR ADQ magma Grain i V quotM C 501uo I Puma mm 7 7 i Ami 2002 precipitatien as a percent of the 19611990 average APRIL 1 SNOWPACK COLORADO STATEWIDE Q N Colorado Statewide Snowpack WMWMNSMOYEL m i m Wilma 1m 7m1 1nul 7am Awning Inehu n Rnawwmr Equlnlm 533 Figux c I Cumulnuu smmudc snmvpmI for Culomdu 1mg 999 20001000 2001200I 10022002 1003 and AV from USDA th SLDIme h r 4 mm streamnaws thousands anteK 1534 was 1992 1911 920 1929 1933 947 was 1965 1914 1963 1992 2am Tlmey Fxgmc 14 nnml am ncmds M m Pondn mm 1m lw pmuu I884 200 The iignrc mm mm L x rcmc lmuglnavmls sud 1 Um m hc mm I950 m uh dmugln 01 mo 10an Now lm lw 1003110 14 hc snmllcsl mine m hc mum mom mm SALN u m 2005 CM mm v 12 um mum 53 3252 258 E 7 s Munlh luusmy 5 a 8 o Annual Flow millions of acrefeet O a N m 1905 a a l915 1925 a m a m o m o m m w v m m m m m m m m m a 1965 a m u p n w m m m Another obvious measurec lea39lllialrloan in US especially Western US is runoff here for the Colorado River showing drought years in for example 1934 when much of US was in extreme drought the Dust Bowl 1977 following one of the least snowy winters ever in the Rockies when I tried to learn how to ski and 2002 the driest year in Colorado Right Glen Canyon at low levels dam in 2003 Chap 3 Risk Perception and Management p 44 Risk probability times consequence We have covered probability Consequence can be measured in many ways as we ll see dollars of damage lives lost Compare consequences and risk 1 X 1000 lives 100 ten year event 01 X 1000 lives 10 one hundred year event 01 X 10000 lives 100 one hundred year event Consequence or impact can often be reduced and risk assessment is almost always assoc1ated With management or mitigation Risk probability X loss mitigation Issues in Risk Management Objective risk vs subjective perceived risk Objective risk assessment from some scientificprofessional analysis standards and best practices in the field replicable Perceived risk by the individual typically lay decisionmaker Principle Lay DM often operate below professional rational level they seek satisfactory rather than optimum outcomes Perceived risk often weighted on consequence Revealed risk tolerance people express their risk tolerance by their behaviorsuse that as a guide to risk management they still live in New Orleans Expressed Risk perceptiontolerance Surveys and other approaches to pin down risk perception and tolerance and willingness to pay for certain reduction of risk or level of acceptable risk Risk Management Conflict between technical and lay approaches Perception affected by Voluntary vs in voluntary Individual vs mass fatalities a priori assumptionsbeliefs Experience Media information Personality eg locus of control risk averse risktaking Role in society J Lquot 39 quot J quot 39 cliff Ilvm m wl nu I quotegsessmem 0nd riSk Percepr39S essmem and risk percepi ammbf dmrcammssemwaJiytyenrcanyplbss es 5 P processespmcesse recessesprocess w 4 439 J I u a A39 w I m o Intumon Statistical intuition Statistic 9 Persona inference Personal inferenc awareness awareneSs UM estim wn MognWIM estimmwml Mognih Cy ex erienc e uency ex erienc equen M 6095 nmngib39eEESi mic cosfs lntangibledg m emu evalug mnulimosvbemw evolug WnUIiWZosib 5 factors anal is Factors analysi Jnity Individuolcommunity Individuulcomml odion policy action policy Risk amplification p 47 see Table 33 Perceived risk markedly higher than objective risk Perceived risk is amplified by concern over consequence RIo p times consequenceX Smith writes it this way R p X LX Where LX loss or consequence and the exponent X is greater than one Surge Risk is Key Risk assessment needed for Longterm hazard assessment preparation Evacuation zones Land use planning Shortterm forecast and warning SLOSH Sea Lake and Overland Surges from Hurricanes Model run for planning and real time forecast see an example here httpwwwnhcnoaaqovHAW2enqlishsurqeslosh2qif Storm Surge factors Pressure low pressure is higher surge Wind speed high speed higher surge Wind direction blowing right angle onto land from water Wind fetch distance wind has blown in relatively straight line across open water allows it to drag more water up against the shore Wind duration longer time wind blows onto shore more water can pile up more chance of surge and high tide occurring simultaneously Shoaling shallow bottom stretching far offshore cause more surge than quick deepening as you go offshore Atlantic coast has steeper shoaling than Gulf where surges are higher Shape of coastline embayments and other concave shapes focus or concentrate the water for high surges headlands and convex shapes shed the water for lower height of surge Mean Eiea Surge is modeled above mean sea level but in realtime forecasting it is added to tide expected at time of max surge Waves are not part of surge height but added as additional hazard Speed direction and fetch all mean surge is highest on right quadrant of a landfalling hurricane The coastline illustrated here is also concave in shape Surge risk maps show area inundated by different Safir Simpson scale hurricanes Maps assume that each spot is just right of eye at landfall Of course not all areas can have that surge in a single storm but forecasting uncertainty means larger areas warned than actually affected man LAKE oxrccnoazz S39ORM macaw monm smw E cumow Cuzco 5 These zones can then be used to plan decideon and organized an evacuation Some areas place storm surge markers to raise awareness maybe especially need in tourist areas where visitors may be unaware Forecast of surge for an actual storm is segmented into different areas with different heights always a range of heig s MW mm MW 39 u 0 WW 39 20 Feet or More 0W LEW 2t05 Fm 1m 3 Feel 2 to 5 Feet mm 1 lo 3 Feel Potential Storm Surge Friday night into Saturday ram snowsinus n Aiiiiude ans KM A A Structural protection can make a difference in surge impact Here Galveston s sea wall built after 1900 storm Left at 1905 construction bottom left in March 2007 with my neighbor for scale and bottom right touched by a notunusually high tide clue to beach erosion Other physical protections include beach nourishment which adds sand is expensive and only marginally effective but also adds recreational space at least until it re erodes Other physical protections include beach armoring with riprap or large rocks Doesn t always do much about surge left but can resist or slow erosion 39 1 effects on 39 39 Homestead FL hm niln e i quotquotme partially protect 4 house Simple cheap ties keep roofs on But shingles and air conditioning units might still come off Hurricane Hazard Mitigation Disaster aid and insurance like other hazards though surge biggest loss is not covered by commercial insurance only thru federal flood insurance Hazard resistant design Shelters 1600 cyclone shelters in Bangladesh after 1992 all new schools in FL are designed as shelters wall and window strength doors interior space raised floors roof engineering facilities etc Building codes widespread and effective Roof construction shingles cladding gutters attached with hurricane clips Roof firmly attached to walls Windows resistant missile impact So FL 4 kg timber striking at 15 ms 33 mph Shinglestiles tested at 49 ms 110 mph Mileti Disasters by Design Disasters by Design A Reassessment of Natural Hazards in the United States by Dennis Mileti A Joseph Henry Press book iSEN 0309518490 375 pages 6 x e 1999 This PDF is available from the Joseph Henry Press at httpwwwnapedulcatalogl5782html DISASiERS Chap 6 Tools for Mitigation httgwwwnagedubooks0309063604htm Chap 6 Tools for Mitigation Five main tools Land use planning and regulation Building codes and standards Insurance Prediction forecast and warning Engineering we don t cover this one Land Use Planning Most promising option since exposure of people and property is main problem but Local government not eager to regulate land Federal and state government not committed and send conflicting signals to local government eg disaster relief and rebuilding federal funding for engineering solutions investment in infrastructure for development etc Barriers to Land Use Planning Hazards not viewed as a problem compared to jobs crime schools etc LU costs can be high immediate but benefits are in future not on my watch Strengthened property rights regime legal protections for property Lucas and political support for property right and against regulatory planning Science and data lackingvery difficult to define location of hazard to allow micro zona on Lack of regional cooperation among fragmented governments occupying the same hazard zone Building Codes Better developed than Land Use regulations well established codes and enforcement tools associated with health and safety They detail dimensions materials performance design operations Three standards Model Building Codes based on Enqineerinq practice standards accepted design fabrication and construction procedures and methods for calculating engineering formulas like wind or snow load etc Materials standards physical properties of building materials Test standards specify tests for durability fire etc Enforcement Major issue states may mandate codes but local government does enforcement Building permit process review inspection and approval Code only as good as enforcement Andrew and other events reveal weaknesses Other problems with codes Most focus on life safety not loss reduction or functionality after a disaster Lack of resources and staff to administer code Stricter state regs often for certain buildings schools hospitals not for residential or commercial which is majority of property at risk Insurance Good logic those at risk pay for loss thru premiums But complex coverage some covered fire hail wind etc But floods including hurricane storm surge earthquake avalanches and landslides not What about fire caused by ea hquake Problems Complex interplay of private and federally subsidized insurance and all forms of disaster relief grants loans etc a form of insurance thru the tax system Large underinsurance out there lt50 in especially floodplains and earthquake zones Why Demand Perceived premiums too high for return on investment Future discounting Expect government aid Don t know the risk Why Supply Adverse selection Worstcase catastrophic loss potential multibillion events now routine big liability and potential insolvency State regulation of rates and equity disallows insurers to vary rates among communities and share premiums across states Mitigation via Insurance More potential than currently utilized Limit the availability nonmitigated properties can t get covered Financial incentives rate reductions lowered deductibles and higher coverages Educational programs Prediction Forecast amp Warnings No comprehensive system decentralized across hazards and agencies Uneven ability to issue and convey warnings Improving for floods tornadoes and hurricanes Moderate success for tsunamis and landstes Problematic for droughts avalanches earthquakes droughts and volcanoes Warning response Good research base now Good knowledge on compliance like evacuation but less on protection choices Improvements will come from Coordination of agencies systemic approach better dissemination Preevent education Wording or message content mm A 1 my immum an response m wquot m SDlid base 0f SDCial pm 3732312231 EHL EQZT39 sc39ence research mnmizm Mm th tells us a lot about gt 5m High the effectiveness of gt 533233 2325 52 warning messages 39 3512 35x 515 Issues include Salim 31 nature 0f the if i l i232 32 5 Mum sage eg th speci city context HE 539 r SW 3526 35 also gets physical l 333 cues that backup Vim kw t e message like 39 Hm rIsIng waterU and in LW social 33 5quot characteristics of the mix 3 n recewer HZ g 9mm Mum W m 0mm Mum smmmim u h soURcE mg and some luau Problems with FWS Officials often slow to decide to issue warnings Ethical issues sources control of info Expectations of panic if warned about low probhigh consequence event so officials withhold info Measuring EQ Magnitude Ancient cultures knew about seismic waves some recorded them The attempt to measure EQ magnitude illustrates problems with measuring any geophysical event some arbitrary benchmarks are created to allow intercomparison Easier than some hazards because EQ s send out longdistance signals measured all over the world Seismology Modern development by Charles Richter who created the first universal scale for measuring EQs Richter Magnitude based on amplitude of seismic waves Openedended each whole number is an order of magnitude X10 increase in energy released Empirically 3 can be felt 4 starts light damage 56 significant damage starts 7 major damage How measured Support moves Demanding job amplify small waves ltmm to see on chart b larg 39 39 ut dampen er a a marhinn breaks Do this for p s and various long waves approaching at different azimuths nswer a a 39 mans Imer laser and digital technology A A r waves 39 eimnnram am 39 39 waves allows triangulation of epicenter Richter measured amplitude of waves radiating from epicenterfocus His original scale was based on So Calif conditions and normalized to a specific design of seismograph at a specified 100km from epicenter Scale built off of empirical attenuation of amplitudes collected by Richter in the 1930s 50s He developed look up charts for a standard seismogram First time difference between P and 8 wave arrival gave you distance to the focusepicenter AMPLITUDE 423 mm ii ililmlirmlirllllin U 111 NJ Then measure the amplitude of the actual trace on a standard 5432 seismometer atm Btj Finally interpolate between the two and you get the Richter magnitude again based on 39 a 5 empirical conditions for southern 5339 a 2 California but not too far off for W a a most of the world s seismic 1 2 455 zones 1 cl 2390 2 r 01 539 u Ami erqu DISTANCE MAGNITQJDE mm km SP TIME s g Modern Richter standard is called the local magnitude ML Log of standard seismograph trace in micrometers 10393 mm normalized to 100 km distance from epicenter eg 1 mm amplitude log10 of 1000 ML3 Energy release of EQ increases X 10 with each whole number increase in MLthough actual ground motions can t increase that much Rather larger areas are shaken with the extra energy Richter is all about energy released at the rupture of a fault and though obviously related it does not imply actual ground shaking which is what really matters in terms of hazards Another scale Mercalli was developed to categorize the surface effects of an earthquake all affected by magnitude of waves type of surface and type of human use MODIFrED HERCAUJ SCALE RICHTER 7quot 39 39 39 rallymtfalnbm Felt by almas name v Eymypeuple WI Fell indoors Y has struck the building quotsf Felt by nearly m 39 awakened I 39 may he 7 VI Flait f a ny peapl emh Furniture malted 61er VII Everyone runs outdoors 39 39 Emma s camiderahly damage elsewhm VIII speciallydesigmdmcmmr 39 f39 39 ng f slightly other collapse 7 39 Ix All bulldlngscunsldeirahly 39 7 shift oll39 foundations MawIIth News 3 Many gm 1 39 W is badly v X39If mmEEVSH s ucmr s ll XII Total deszrum on objects m tumbled and recorded on seismometers Fe rwa Dawns u H mm nu um um may summed ables m away Many frightened and run nutdnors pm an W m madam mma s mm pufas m chimneys mmavs m Everynne runs outdnorsquot Drivers of autns disturbed Waves seen on grnund line nf sight distnrted mme unvessmanumm smace huesafa nmwamm wwmw wpmw EQ Hazard Assessment Richter is insufficient for hazard assessment too much attention to the geophysical phenomenon energy release making EQ comparable but not linked to likely damage on the surface Mercalli is a measure of what actually results in a given situation but how applicable to say LA What really matters to hazard assessment Ground motions caused by waves moving through different materials amp geographical settings and Likely damage And like all risk assessment we re interested in frequencyprobability duration locationaldetails and local impacts like ground failure liquefaction landslide etc Ground Motions Box 52 Seismologist and hazards mangers have settled on a key measure of ground motions Motion measured as peak or instantaneous acceleration in g s acceleration due to gravity 98 msz 1g may do in some bldgs unreinforced masonry 2 causes more damage 5 is Kobelike damage gt5 g is major motion What the heck is Acceleration and acceleration due to G anyhow Acceleration change in speed over time often instantaneous or short period measured compared to a falling object at sea level which speeds up at 98 mss aka 98ms2 aka 321 ftS392 Why use it Common factor in engineering force evaluation so also a measure of force applied or load factor Easy to measure drop something at sea level and record It Also eaSIly available accelerometers Experienced by people in planes and cars and spaceships up to 39s in short episodes in some rides only 3 g s on Space Shuttle for equipment s sake sports car starting 03 05 gt 09 braking 08 10 gt 13 06 cornering 06 10 gt 25 Awkward measure for earthquake shaking but you can imagine it think in terms of distance moved 321 fts2 not too uncommon in amusement parks So a 1g ground motion would move you 3 feet in a second And a 5g ground motion moves you 16 feet in a second Now that is major destruction Here s example ground motion risk mapwe go over steps in EQ risk assessment in next lecture Shaking g Pga Peak Ground Acceleration Firm Rock I lt 10 1O 20 I 20 30 I 30 40 I 40 50 I 50 60 I 60 70 7 70 80 gt 80 The unit quot9quot is acceleration of gravity Problem expressing magnitude vs probability in useful way USGS has settled on a mixed p and r relative to a peak or exceedance magnitude 10 chance p in 50 years 1 chance in 5 years 20 chance in 100 years Return period about 500 years This must be the cumulative p from all possible sources of shakingthat s a lot in some areas especially CA where this was designed The USGS Fine Print These maps depict earthquake hazard by showing by contour values the earthquake ground motions that have a common given probability of being exceeded in 50 years The ground motions being considered at a given location are those from all future possible earthquake magnitudes at all possible distances from that location The ground motion coming from a particular magnitude and distance is assigned an annual probability equal to the annual probability of occurrence of the causative magnitude and distance The method assumes a reasonable future catalog of earthquakes based upon historical earthquake locations and geological information on the recurrence rate of fault ruptures When all the possible earthquakes and magnitudes have been considered one can find a ground motion value such that the annual rate of its being exceeded has a certain value Hence on a given map for a given probability of exceedance E locations shaken more frequently will have larger ground motions For a LARGE exceedance probability the map will show the relatively likely ground motions which are LOW ground motions because small magnitude earthquakes are much more likely to occur than are large magnitude earthquakes For a SMALL exceedance probability the map will emphasize the effect of less likely events larger magnitude andor closerdistance events producing overall LARGE ground motions on the map The maps have this format because they are designed to be useful in building codes in which we assume that for the most part all buildings would be built to the same level of safety For other applications maps of another format might be more useful For instance many buildings across the US are built more or less the same regardless of earthquake hazard lfwe knew that a particulartype of building was likely to fail at a particular ground motion level we could make a map showing contours of the likelihood of that ground motion value being exceeded due to earthquakes What is the likelihood of a large earthquake at location X Our analyses do not answer your question as stated quotprobability of large earthquake at a locationquot but in a more suitable manner for safety Danger comes not only from large earthquakes AT a location but also large earthquakes further away and close smaller earthquakes Inasmuch as smaller earthquakes are more likely to occur some attention has to be paid to the contribution to hazard from these events too By focusing on GROUND SHAKING caused by earthquakes of all magnitudes and distances from the site rather than the size of the earthquake quotatquot a site we get a truer picture of the hazard The maps give a good impression of overall relative earthquake ground motion shaking hazard for various locations in the vicinity ofthe locations you are interested You can see which locations look more or less hazardous than others More particularly our maps give the probability of various levels of ground motion being exceeded in 50 years For instance using the data available at our web site for Chico California and for San Diego California one can get an idea of the approximate probability of strong damaging ground motion at each location Inspecting peak ground acceleration maps for ground motions having 10 percent probability of being exceeded in 50 years and ground motions having 2 percent probability of being exceeded in 50 years we would find approximately that around San Diego the ground motion that has 10 percent probability of being exceeded in 50 years is about equal to the ground motion around Chico that has 2 percent probability of being exceeded in 50 years That ground motion is 30 percent 9 See the data from the zipcode lookup below From one of the answers at the FrequentlyAsked Questions page at our site ltlt2What is quot Qquot What is the relation to building damage gtgt we find that an approximate threshold for shaking that causes damage is 10 percent 9 So 30 percent 9 is very strong shaking indeed and has about 1 chance in 10 of occurring in San Diego in 50 years In 20 years this would be about 1 chance in 25 In Chico this level of shaking has about 1 chance in 50 of occurring in 50 years or about 1 chance in 125 in 20 years This may be a reasonable number to use for the likelihood ofthe occurrence of a big nearby earthquake What is quot 9 When acceleration acts on a physical body the body experiences the acceleration as a force The force we are most experienced with is the force of gravity which caused us to have weight The units of acceleration ofthe map are measured in terms ofg the acceleration due to gravity An acceleration of11 feet per second per second is 1112 254 335 cmseclsec The acceleration due to gravity is 980 cmseclsec so an acceleration of 11 feetsecsec is about 335980 0 Expressed as a percent 034 g is 34 A g What is the relation to buil ing damage PGA 9 g 80 60 40 20 May be approxlmale threshold ol damage 3 to older prelges dwelllngs rdwelll gs t0 reslsl earl e note at bottom ol page Pre1940 dwellings are likely to perform poorly in earthquake shaking Pre1975 dwellings are likely to have some vulnerabilities to earthquake shaking 40 welinn i r v r severe shaking 60 A g with only chimney damage and damage to contents You can see EQ hazard maps and create your own here httpearthquakeusgsgovresearchhazm apsindexphp httpearthquakeusgsgovresearchhazm apsdesignindexphp Peak Acceleration gwilh 2 Probability of Exceedance in 50 Vears uses Map on 2002rev 39W 120w mnw 115w NW NW Peak Acceleration gwilh10 Probability of Exceedance in 50 Vears use Map on 2002rev 05w 2quot W 115w How ms w 100W


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