Glendale (PDF) - Hazard Mitigation Web Portal - State of California

More documents

Recommendations

Info

Natural Hazards Mitigation PlanCity of Glendale, CaliforniaSection 6 – EarthquakesLanders and Big Bear Earthquakes of 1992On the morning of June 28, 1992, most people in southern California were awakened at 4:57 by thelargest earthquake to strike California in 40 years. Named “Landers” after a small desert communitynear its epicenter, the earthquake had a magnitude of 7.3. More than 50 miles of surface ruptureassociated with five or more faults occurred as a result of this earthquake. The average right-lateralstrike-slip displacement was about 10 to 15 feet, but a maximum of 18 feet of slip was observed.Centered in the Mojave Desert, approximately 120 miles from Los Angeles, the earthquake causedrelatively little damage for its size (Brewer, 1992). It released about four times as much energy asthe very destructive Loma Prieta earthquake of 1989, but fortunately, it did not claim as many lives(one child died when a chimney collapsed). The power of the earthquake was illustrated by thelength of the ground rupture it left behind. The earthquake ruptured 5 separate faults: JohnsonValley, Landers, Homestead Valley, Emerson, and Camp Rock faults (Sieh et al., 1993). Nearbyfaults also experienced triggered slip and minor surface rupture. There are no Modified MercalliIntensity (MMI) reports for this earthquake in the Glendale area, but in Pasadena three individualsreported MMIs of IV, and in Burbank, MMIs of IV to V were reported(http://pasadena.wr.usgs.gov/shake/ca/).The magnitude 6.4 Big Bear earthquake struck little more than 3 hours after the Landers earthquakeon June 28, 1992 at 8:05:30 A.M. PDT. This earthquake is technically considered an aftershock ofthe Landers earthquake (indeed, the largest aftershock), although the Big Bear earthquake occurredover 20 miles west of the Landers rupture, on a fault with a different orientation and sense of slipthan those involved in the main shock. From its aftershock, the causative fault was determined to bea northeast-trending left-lateral fault. This orientation and slip are considered “conjugate” to thefaults that slipped in the Landers rupture. The Big Bear earthquake did not break the groundsurface, and, in fact, no surface trace of a fault with the proper orientation has been found in the area.The Big Bear earthquake caused a substantial amount of damage in the Big Bear area, butfortunately, it claimed no lives. However, landslides triggered by the quake blocked roads in themountainous areas, aggravating the clean-up and rebuilding process (SCEC-DC, 2001).Northridge Earthquake of 1994The Northridge Earthquake of January 17, 1994 woke up most of southern California at 4:30 in themorning. The earthquake’s epicenter was located 20 miles to the west-northwest of downtown LosAngeles, on a previously unknown blind thrust fault now called the Northridge (or Pico) Thrust.Although moderate in size, this earthquake produced the strongest ground motions everinstrumentally recorded in North America. The M w 6.7 earthquake is one of the most expensivenatural disasters to have impacted the United States. Damage was widespread, sections of majorfreeways collapsed, parking structures and office buildings collapsed, and numerous apartmentbuildings suffered irreparable damage. Damage to wood-frame apartment houses was verywidespread in the San Fernando Valley and Santa Monica areas, especially to structures with "soft"first floor or lower-level parking garages. The high accelerations, both vertical and horizontal, liftedstructures off of their foundations and/or shifted walls laterally. The death toll was 57, and morethan 1,500 people were seriously injured.In the Glendale area, this earthquake caused predominantly Modified Mercalli intensities of VII(http://pasadena.wr.usgs.gov/shake/ca/). High-profile damage in Glendale includes the followingcases: A section of the third level above grade in the Glendale City Center parking structurecollapsed, sections of the Glendale Galleria parking structure settled 4 to 8 inches due to damage topedestals, and the Glendale Fashion Center had damage to exterior columns.Despite the losses, gains made through earthquake hazard mitigation efforts of the last two decadeswere obvious. Retrofits of masonry building helped reduce the loss of life, hospitals suffered lessstructural damage than in 1971 San Fernando earthquake, and emergency response was exemplary.2006 PAGE 6 - 13
Natural Hazards Mitigation PlanCity of Glendale, CaliforniaSection 6 – EarthquakesEarthquake Hazard AssessmentChoosing Earthquakes for Planning and DesignIt is often useful to create a deterministic or design earthquake scenario to study the effects of aparticular earthquake on a building or a community. Often, such scenarios consider the largestearthquake that is believed possible to occur on a fault or fault segment, referred to as the maximummagnitude earthquake (Mmax). Other scenarios consider the maximum probable earthquake(MPE) or design basis earthquake (DBE) (1997 Uniform Building Code - UBC), the earthquakewith a statistical return period of 475 years (with ground motion that has a 10 percent probability ofbeing exceeded in 50 years). For public schools, hospitals, and other critical facilities, the CaliforniaBuilding Code (1998) defines the Upper Bound Earthquake (UBE), which has a statistical returnperiod of 949 years and a ground motion with a 10 percent probability of being exceeded in 100years. As the descriptions above suggest, which earthquake scenario is most appropriate depends onthe application, such as the planned use, lifetime or importance of a facility. The more critical thestructure, the longer the time period used between earthquakes and the larger the design earthquakeshould be.Geologists, seismologists, engineers, emergency response personnel and urban planners typically usemaximum magnitude and maximum probable earthquakes to evaluate seismic hazard. Theassumption is that if we plan for the worst-case scenario, we establish safety margins. Then smallerearthquakes, that are more likely to occur, can be dealt with effectively.Seismic design parameters define what kinds of earthquake effects a structure must be able towithstand. These include peak ground acceleration, duration of strong shaking, and the periods ofincoming strong motion waves.As is true for most earthquake-prone regions, many potential earthquake sources pose a threat toGlendale. Thus it is also important to consider the overall likelihood of damage from a plausiblesuite of earthquakes. This approach is called probabilistic seismic hazard analysis (PSHA), andtypically considers the likelihood of exceeding a certain level of damaging ground motion that couldbe produced by any or all faults within a 100-km radius of the project site, or in this case, the City.PSHA is utilized by the U.S. Geological Survey to produce national seismic hazard maps that areused by the Uniform Building Code (ICBO, 1997).Regardless of which fault causes a damaging earthquake, there will always be aftershocks. Bydefinition, these are smaller earthquakes that happen close to the mainshock (the biggest earthquakeof the sequence) in time and space. These smaller earthquakes occur as the Earth adjusts to theregional stress changes created by the mainshock. The bigger the mainshock, the greater thenumber of aftershocks, the larger the aftershocks will be, and the wider the area in which they mightoccur. On average, the largest aftershock will be 1.2 magnitude units less than the mainshock. Thisis an average, and there are many cases where the biggest aftershock is larger than the averagepredicts. The key point is this: any major earthquake will produce aftershocks large enough to causeadditional damage, especially to already-weakened structures. Consequently, post-disaster responseplanning must take damaging aftershocks into account.Hazard IdentificationIn California, many agencies are focused on seismic safety issues: the State’s Seismic SafetyCommission, the Applied Technology Council, Governor’s Office of Emergency Services, UnitedStates Geological Survey, Cal Tech, the California Geological Survey as well as a number ofuniversities and private foundations. These organizations, in partnership with other State andFederal agencies, have undertaken a rigorous program in California to identify seismic hazards and2006 PAGE 6 - 14
Page 2 and 3:
City CouncilDave Weaver, MayorRafi
Page 4 and 5:
Natural Hazards Mitigation PlanCity
Page 6 and 7:
Page 8 and 9:
Page 10 and 11:
Page 12 and 13:
Page 14 and 15:
Page 16 and 17:
Page 18 and 19:
Page 20 and 21:
Page 22 and 23:
Page 24 and 25:
Page 26 and 27: Natural Hazards Mitigation PlanCity
Page 56 and 57: Table 4-2: STAPLEE Ranking of Actio
Page 58 and 59: Table 4-4: Description of Ranking C
Page 108 and 109: Natural Hazards Mitigation Plan Sec
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
Page 198 and 199:
Page 200 and 201:
Page 202 and 203:
Page 204 and 205:
Page 206 and 207:
Page 208 and 209:
Page 210 and 211:
Page 212 and 213:
Page 214 and 215:
Page 216 and 217:
Page 218 and 219:
Page 220 and 221:
Page 222 and 223:
Page 224 and 225:
Page 226 and 227:
Page 228 and 229:
Page 230 and 231:
Page 232 and 233:
Page 234 and 235:
Page 236 and 237:
Page 238 and 239:
Page 240 and 241:
Page 242 and 243:
Page 244 and 245:
Page 246 and 247:
Page 248 and 249:
Page 250 and 251:
Page 252 and 253:
Page 254 and 255:
Page 256 and 257:
Page 258 and 259:
Page 260 and 261:
Page 262 and 263:
Page 264 and 265:
Page 266 and 267:
Page 268 and 269:
Page 270 and 271:
Page 272 and 273:
Page 274 and 275:
Page 276 and 277:
Page 278 and 279:
Page 280 and 281:
Page 282 and 283:
Page 284 and 285:
Page 286 and 287:
Page 288 and 289:
Page 290 and 291:
Page 292 and 293:
Page 294 and 295:
Page 296 and 297:
Page 298 and 299:
Page 300 and 301:
Page 302 and 303:
Page 304 and 305:
Page 306 and 307:
Page 308 and 309:
Page 310 and 311:
Page 312 and 313:
Page 314 and 315:
Page 316 and 317:
Page 318 and 319:
NOTES:This map is intended for gene
Page 325:
Page 329 and 330:
Page 332 and 333:
City of GlendaleUpdateHazard Mitiga
Page 334 and 335:
Similar to Safety ElementIncludesEa
Page 336 and 337:
HospitalsPartnershipsWithin City an
Page 338 and 339:
Impact on CityMost significant area
show all

Glendale (PDF) - Hazard Mitigation Web Portal - State of California

Create successful ePaper yourself

Delete template?

Save as template?