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For designing buildings and other structures to safely resist earthquakes, the 2009 National Earthquake Hazards Reduction Program (NEHRP) Recommended Seismic Provisions and the 2010 American Society of Civil Engineers, Structural Engineering Institute (ASCE/SEI) 7 Standard contain maps of Risk-Targeted Maximum Considered Earthquake (MCER) spectral response accelerations, Maximum Considered Earthquake Geometric Mean (MCEG) peak ground accelerations, and long-period transition periods (TL). The MCER ground motions are also in the 2013 ASCE/SEI 41 Standard and the 2012 and 2015 editions of the International Building Code. The MCER, MCEG, and TL maps are derived from the U.S. Geological Survey (USGS) National Seismic...
Please see the parent item for a high-level description. For designing buildings and other structures to safely resist earthquakes, the 2009 NEHRP Recommended Seismic Provisions and the 2010 ASCE/SEI 7 Standard contain maps of Uniform Hazard response accelerations, risk coefficients, 84th-percentile (deterministic) spectral accelerations, and Risk-Targeted Maximum Considered Earthquake (MCER) spectral response accelerations (Ss and S1), all at spectral periods of 0.2-second and 1.0-second. The spectral accelerations are for the direction of maximum horizontal response and a site average shear wave velocity within 30 m of the surface (VS30) of 760 m/s, in units of percent of the acceleration of gravity (g). For...
The Golden cluster is named after the Golden Triangle region of southeast Asia, centered roughly on the intersection of Thailand, Laos and Myanmar. The cluster includes five major earthquakes in that region: the May 16, 2007 Bokeo, Laos, event (Mw 6.3); the March 24, 2011 Tarlay, Myanmar, earthquake (Mw 6.9); the May 5, 2014 Mae Lao event (6.2 Mw) in Chiang Rai Province, Thailand; the November 20, 2019 Sainyabuli event (6.2 Mw) in Laos; and the July 21, 2022 Keng Tung, Myanmar, earthquake (5.9 Mw). The Mae Lao sequence has been closely studied by Pananont, P., et al. (2017), Seismotectonics of the 2014 Chiang Rai, Thailand, earthquake sequence, J. Geophys. Res. Solid Earth, 122, 6367–6388, doi:10.1002/2017JB014085....
The Bejaia cluster is named for the coastal city of Béjaïa, Algeria. The rate of seismicity is rather high and many events are recorded at teleseismic distances but there are no events with magnitude 6 or greater in the cluster. Because seismograph stations are somewhat spread out in this region it was necessary to keep the cluster a big larger (geographically) than usual in order to obtain the necessary azimuthal coverage. This cluster is quite unusual in that the arrival time dataset from the ISC contains almost no S-picks at epicentral distances less than about 3°. The lack of local-distance S-phase data compromises the resolution of the hypocentroid to some extent but the location calibration is still good....
The Scarzana cluster is named for the village Scarzana in the province of Forlì-Cesena, northeast italy, southeast of Bologna, northeast of Florence. The region is very well instrumented and seismically active at lower magnitudes, up to around M5, so the calibration analysis proceeded quite easily. Some events in the area are as deep as 70 km, but the cluster was restricted to events with depths less than 30 km. All events have depth control from near-source or local distance readings and many also have a few teleseismic depth phases that are in good agreement with those depths. The earthquakes are mainly in the central mountains but for a few events near the Adriatic coast there are some raypaths to local stations...
The Coalinga cluster is named for the town of Coalinga, California, which itself was named after "Coaling Station A" on the old railway line through that area. The cluster is small in number (26) but contains several important earthquakes, including the 6.5 Mw Coalinga event on May 2, 1983 and the 6.5 Mw San Simeon event on December 22, 2003. The source area includes the famous "Parkfield" section of the San Andreas Fault. The cluster includes the most recent "repeating" earthquake on this section, the 6.0 Mw event on September 28, 2004, but the arrival time data for the previous event, on June 28, 1966, were inadequate to obtain a stable solution, other than confirming its origin at the northwest end of the aftershock...
The Socorro cluster is named for the city of Socorro, New Mexico, U.S.A. The seismicity is associated with the Rio Grande Rift. Most of the events are small, and the cluster has few readings beyond ~1000 km. Many events were well recorded by the Transpotable Array when it moved through the region, so the location calibration is very robust. All events have depth control from near-source or local-distance readings. Number of events: 39 Calibration type: direct calibration using data to 0.8 degrees; hypocentroid calibration level = 0.6 km Epicentral calibration range: 1 - 2 km Date range: 19891129...
The Karonga cluster is named for the township of Karonga, Malawi on the northwest shore of Lake Malawi (also known as Lake Nyasa and Lake Niassa) in the East African Rift Zone. Over half of the 44 events in the cluster are asociated with a series of earthquakes near Karonga in late 2009, the largest being an Ms 6.0 event December 19, 2009 and several having magnitudes in the 5.5-5.8 range. Although these events (and all others in the cluster) were well-recorded at far-regional and teleseismic distances, there are almost no local-distance arrivals with which to do a calibrated relocation of this cluster, with one exception, an Ms 3.5 event (April 9, 2015) on the other side of the lake, in Tanzania, which was very...
The Karbaas cluster is named after a village in the Zagros Mountains of Iran, southwest of Shiraz. This cluster includes three events greater than magnitude 5.5: two 5.8 events in 1994 (March 1 and June 20) and a 6.4 event on May 6, 1999 (which heavily damaged the village of Karbaas). The area has been very active seismically at lower magnitudes, especially in recent years. The calibration data set includes a large number of S-P readings from accelerometer stations and these data contribute much of the coverage in the south and southwest. A.R. Ghods repicked many of the arrival times from Iranian networks, including the S-P data from the INSM network of accelerometers (BHRC). The focal depth of most events in the...
The Farsan cluster is named after the city of Farsan in Chaharmahal and Bakhtiari Province, Iran. This cluster consists of mostly moderate magnitude events (up to Mw 6) and covers ~40 years of seismicity. A. Ghods repicked many of the arrival times from Iranian networks, including S-P data from the INSM network of accelerometers (BHRC). This cluster greatly benefited from these S-P picks for the focal depth estimation: 46 events are constrained by near-distance picks, 36 by local distance picks. The remainder of the events are held at a default focal depth of 14 km. Further information about this cluster is contained in Karasözen et al. (in preparation), Seismotectonics of the Zagros (Iran) from orogen-wide earthquake...
The Haicheng cluster is named for the city of Haicheng in Liaoning Province, northeastern China. The cluster is based on the Ms 7.5 earthquake of February 4, 1975. Arrival time data is sparse for this cluster, limiting it to 34 earthquakes. Only 13 of the events have readings within the 1.2° epicentral distance range chosen for estimation of the hypocentroid but the location calibration is reasonably good. Some events have depth constraint from teleseismic depth phases, but almost half the events are fixed at the default depth of 15 km, the median depth of the events which do have depth control. ...
The Bojnurd cluster is named for the city of Bojnord in the North Khorasan province, Iran. This cluster mostly consists of moderate-sized recent events (M<6) but also includes the MS 6.8 earthquake on July 30, 1970 and the MS 6.6 event on February, 4 1997. The geographic extent of the cluster is larger than usual in order to have acceptable azimuthal coverage for the hypocentroid. A.R. Ghods repicked many of the arrival times from Iranian networks, including S-P data from the INSM network of accelerometers (BHRC). Focal depths of 103 events are constrained by near- and local-distance readings; the remaining 74 events are held at the default depth of 16 km. Further information about this cluster is contained in:...
The DBZ (Dasht-e-Bayaz-Zirkuh) cluster is based on several sequences of strong earthquakes along the Dasht-e-Bayaz and Abiz faults in eastern Iran, including the the Dasht-e-Bayaz earthquake (Mw 7.1) on August 31, 1968, the Mw 6.3 Ferdows event on September 1, 1968, the Ms 6.2 Qayen event on November 7, 1976, the Mw 6.5 Boznabad event on January 16, 1979, the Mw 6.6 Korizon/Ghaenat event on November 14, 1979, the Mw 7.1 Khuli-Boniabad event on November 27, 1979, the Mw 5.9 Kalat-e-Shur event on December 7, 1979 and the Mw 7.3 Zirkuh/Ardekul/Ghaen-Birjand event on May 10, 1997. Calibration is greatly aided by arrival time readings from the Khorasan Network (Ferdowsi University). A.R. Ghods repicked many of the arrival...
The Ridgecrest cluster is named for the town of Ridgecrest in California, U.S.A. The cluster is based on major earthquake sequence that began on July 4, 2019 with a 6.4 Mw event, followed two days later by a 7.1 Mw event. The cluster includes earlier seismicity in the region, all of moderate magnitude. Arrival time data for these earlier events is from the ISC Bulletin. The July 2019 sequence uses arrival time data mainly from the NEIC, but a few of the larger events also have some data from the ISC. The cluster could be relocated fairly well with free depth but the final runs were done with depth fixed because of instability in a few events. Because of the extremely dense network of stations in this region, the...
The Cheneville cluster is named for the town of Chénéville, northeast of Ottawa, Canada. The cluster includes one moderate-sized event (5.4 mb, on June 23, 2010) with an extensive aftershock sequence. Most other events in the cluster range in magnitude from ~2-4. Only a few events are recorded beyond near-regional distances. Station coverage at local distances is excellent and focal depths for all events are well constrained. Number of events: 60 Calibration type: direct calibration using data to 1.2 degrees; hypocentroid calibration level = 0.3 km Epicentral calibration range: 0 - 1 km Date range: 19871111 - 20141117 Latitude range: 45.457 - 46.321 Longitude range: -75.750 - -74.546 Depth range: 4.0...
The Levin cluster is named for the town of Levin, on the southwestern coast of North Island, New Zealand. The cluster includes moderate-sized events (magnitude 4 and 5) distributed fairly evenly over depths from less than 10 km to almost 60 km, almost all of which are observed at teleseismic distances. Most events have depth control fron near-source arrival times. The local seismograph network is dense and well-distributed in azimuth from the cluster, making the location calibration very robust. Number of events: 45 Calibration type: direct calibration using data to 0.8 degrees; hypocentroid calibration...
The RVZ cluster is named for the Reykjanes Volcanic Zone in southwestern Iceland. The cluster does not include events in the South Island Seismic Zone immediately to the east because initial attempts to include events from both source regions led to inconsistencies, likely due to changing crustal velocity characteristics. Since 2006 data is available for a number of seismic stations in the Reykjanes Volcanic Zone that provde very strong location calibrations, so the cluster is restricted to events since that time. Because of the uniformly good station coverage, this cluster can be relocated with free depth. There are no events deeper than ~10 km and there is a peak of activity near 5 km depth. ...
Compiled Vs30 measurements obtained by studies funded by the U.S. Geological Survey (USGS) and other governmental agencies. Thus far, there are 2,997 sites in the United States, along with metadata for each measurement from government-sponsored reports, Web sites, and scientific and engineering journals. Most of the data originated from publications directly reporting the work of field investigators. A small subset (less than 20 percent) of Vs30 values was previously compiled by the USGS and other research institutions. Whenever possible, Vs30 originating from these earlier compilations were crosschecked against published reports. Both downhole and surface-based Vs30 estimates are represented. Most of the VS30 data...
Types: Citation;
Tags: Earth,
Earthquake Hazards Program,
GHSC,
Geologic Hazards Science Center,
USGS,
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