Modern Modeling Determines Magnitudes of Historic Earthquakes

2020 ◽  
Author(s):  
Lauren Milideo
Keyword(s):  
Author(s):  
Susan Elizabeth Hough ◽  
Roger G. Bilham

Earthquakes rank among the most terrifying natural disasters faced by mankind. Out of a clear blue sky-or worse, a jet black one-comes shaking strong enough to hurl furniture across the room, human bodies out of bed, and entire houses off of their foundations. When the dust settles, the immediate aftermath of an earthquake in an urbanized society can be profound. Phone and water supplies can be disrupted for days, fires erupt, and even a small number of overpass collapses can snarl traffic for months. However, when one examines the collective responses of developed societies to major earthquake disasters in recent historic times, a somewhat surprising theme emerges: not only determination, but resilience; not only resilience, but acceptance; not only acceptance, but astonishingly, humor. Elastic rebound is one of the most basic tenets of modern earthquake science, the term that scientists use to describe the build-up and release of energy along faults. It is also the best metaphor for societal responses to major earthquakes in recent historic times. After The Earth Quakes focuses on this theme, using a number of pivotal and intriguing historic earthquakes as illustration. The book concludes with a consideration of projected future losses on an increasingly urbanized planet, including the near-certainty that a future earthquake will someday claim over a million lives. This grim prediction impels us to take steps to mitigate earthquake risk, the innately human capacity for rebound notwithstanding.


1991 ◽  
Vol 81 (6) ◽  
pp. 2289-2309
Author(s):  
Allison L. Bent ◽  
Donald V. Helmberger

Abstract The high level of seismic activity and the potential for large earthquakes in the San Jacinto fault zone, southern California, make it desirable to have accurate locations and source parameters for as many previous events as possible. Prior to the installation of a dense seismic network in this region, earthquakes were located using only a few stations with generally poor azimuthal coverage resulting in considerable uncertainty in the locations. We relocate and obtain moment estimates for historic (pre-WWSSN) earthquakes in the western Imperial Valley by comparing the waveforms and travel times with recent earthquakes in the region. All the events are in the ML 5.5 to 6.5 range. The historic earthquakes of interest occurred in 1937, 1942, and 1954. We use the 1968 Borrego Mountain, 1969 Coyote Mountain, and 1987 Elmore Ranch earthquakes as calibration events. We employ regional and teleseismic data from continuously operating stations, with Pasadena, DeBilt, Berkeley, Ottawa, and St. Louis recording most of the events. The waveforms imply that all the events are almost pure strike-slip events on vertical or near-vertical faults. Approximate values for the strikes were obtained and are within the range of observed strikes for well-studied earthquakes in this region. The earthquakes are relocated by comparing S-P and surface-wave - S travel times of historic events with the presumably well-located recent events. The relocations require only a small change in location for the 1954 event and a larger adjustment in the 1942 epicenter. It also appears that the 1969 earthquake may have been mislocated. The moment estimates are obtained by direct comparison of the maximum amplitudes. The moment estimates imply that the 1968 and not the 1942 earthquake is the largest to have occurred in the region this century. Previous magnitude estimates suggested the 1942 event was larger.


2016 ◽  
Vol 121 (1) ◽  
pp. 2-16 ◽  
Author(s):  
Bruno Wilhelm ◽  
Jerome Nomade ◽  
Christian Crouzet ◽  
Camille Litty ◽  
Pierre Sabatier ◽  
...  

Radiocarbon ◽  
2001 ◽  
Vol 43 (3) ◽  
pp. 1147-1154 ◽  
Author(s):  
Hendrik J Bruins

Chronology is the backbone of all history, as the flow of time is identical in scholarly and scientific fields, even in the Near East. Radiocarbon dating can provide an essential and unifying chronological basis across disciplines, despite precision limitations. This issue presents exciting new 14C developments in archaeological and environmental contexts, ranging from Proto-Neolithic cultures to historic earthquakes along the Dead Sea. Dark periods devoid of settlement in the deserts of the southern Levant seem to disappear with 14C dating. Significant new findings collectively indicate the need for major chronological revisions in the 4th and 3rd millennia BCE in Egypt and the Levant. The implications for the 2nd millennium BCE are not yet established, but the use of 14C dating in the Iron Age is finally beginning to focus on current controversies. The chronological way forward for Dynastic Egypt and the Levantine Bronze and Iron Ages is a multi-disciplinary approach based on detailed high-quality 14C series as a unifying time foundation to anchor archaeological, textual, and astronomical data.


2021 ◽  
Author(s):  
Aurelia Hubert-Ferrari ◽  
Jasper Moernaut ◽  
Revital Bookman ◽  
Nicolas Waldmann ◽  
Nadav Wetzler ◽  
...  

<p>Seismogenic turbidites are widely used for geohazard assessment. The use of turbidites as an earthquake indicator requires a clear demonstration that an earthquake, rather than non-seismic factors, is the most plausible trigger. The seismic origin is normally verified either by correlating the turbidites to historic earthquakes, or by demonstrating synchronous deposition over large areas of a basin. Correlating historic earthquakes could potentially constrain the seismic intensities necessary for triggering turbidites, however this method is not applicable to prehistoric events. In addition, the synchronous deposition of turbidites cannot be verified for a single core record.</p><p>Here, we propose a new approach to establish the seismic origin of prehistoric turbidites that involves analyzing in situ deformation that underlies each turbidite, as recorded in a 457 m-long core from the Dead Sea depocenter. These in situ deformations have been previously verified as seismites and could thus authenticate the trigger for each overlying turbidite. We also constrain the seismic intensities that triggered prehistoric turbidites by analyzing the degree of in situ deformation underlying each turbidite. Moreover, our high-resolution chemical and sedimentological data validate a long-lasting hypothesis that soft-sediment deformation in the Dead Sea formed at the sediment-water interface. In addition, we use our results to propose seven basic earthquake-related depositional scenarios preserved in depocenters located in tectonically active regions like the Dead Sea. These techniques and findings permit a more confident geohazard assessment in the region and act as a model for other similar tectonic settings, by improving the completeness of a paleoseismic archive.</p>


Author(s):  
J. R. Arango-Gonzalez

There exists in Spain a body of literature on the subject of historic earthquakes which, due to the lack of adequate analysis of the information available, turns out to be practically worthless. This article investigates the Andalusian Earthquake (25/12/1884). Ground liquefaction is analyzed at five sites within the province of Granada and Malaga, as well as in the damage caused to the Restabal Church. The final conclusions show the minimum acceleration value, which causes both the ground liquefaction as well as damage to the building itself. This research's starting point is taken from historic data found in reports carried out by Official Spanish, Italian and French Commissions sent to study the earthquake. Those documents provide us with information about the damage caused both to the buildings themselves, as well as to the effects on the ground. The geotechnical data needed to check ground liquefaction was obtained by penetration tests. The mechanical characteristics and resistance of the materials of the building, essential for the analysis of their seismic resistance, were taken from samples carried out in the laboratory on the same materials or from already existing data from similar materials.


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