Contrasting seismic risk for Santiago, Chile, from near-field and distant earthquake sources

More than half of all the people in the world now live in dense urban centres. The rapid expansion of cities, particularly in low-income nations, has enabled the economic and social development of millions of people. However, many of these cities are located near active tectonic faults that have not produced an earthquake in recent memory, raising the risk of losing hard-earned progress through a devastating earthquake. In this paper we explore the possible impact that earthquakes can have on the city of Santiago in Chile from various potential near-field and distant earthquake sources. We use high-resolution stereo satellite imagery and imagery-derived digital elevation models to accurately map the trace of the San Ramón Fault, a recently recognised active fault located along the eastern margins of the city. We use scenario-based seismic-risk analysis to compare and contrast the estimated damage and losses to the city from several potential earthquake sources and one past event, comprising (i) rupture of the San Ramón Fault, (ii) a hypothesised buried shallow fault beneath the centre of the city, (iii) a deep intra-slab fault, and (iv) the 2010 Mw 8.8 Maule earthquake. We find that there is a strong magnitude–distance trade-off in terms of damage and losses to the city, with smaller magnitude earthquakes in the magnitude range of 6–7.5 on more local faults producing 9 to 17 times more damage to the city and estimated fatalities compared to the great magnitude 8+ earthquakes located offshore in the subduction zone. Our calculations for this part of Chile show that unreinforced-masonry structures are the most vulnerable to these types of earthquake shaking. We identify particularly vulnerable districts, such as Ñuñoa, Santiago, and Providencia, where targeted retrofitting campaigns would be most effective at reducing potential economic and human losses. Due to the potency of near-field earthquake sources demonstrated here, our work highlights the importance of also identifying and considering proximal minor active faults for cities in seismic zones globally in addition to the more major and distant large fault zones that are typically focussed on in the assessment of hazard.

Contrasting seismic risk for Santiago, Chile, from near-field and distant earthquake sources

More than half of all the people in the world now live in dense urban centres. The rapid expansion of cities, particularly in low-income nations, has enabled the economic and social development of millions of people. However, many of these cities are located near active tectonic faults that have not produced an earthquake in recent memory, raising the risk of losing the hard-earned progress through a devastating earthquake. In this paper we explore the possible impact that earthquakes can pose to the city of Santiago in Chile from various potential near-field and distant earthquake sources. We use high resolution stereo satellite imagery and derived digital elevation models to accurately map the trace of the San Ramón Fault, a recently recognised active fault located along the eastern margins of the city. We use scenario based seismic risk analysis to compare and contrast the estimated damage and losses to the city from several potential earthquake sources and one past event, comprising (i) rupture of the San Ramón Fault, (ii) a hypothesised buried shallow fault beneath the centre of the city, (iii) a deep intra-slab fault, and (iv) the 2010 Mw 8.8 Maule earthquake. We find that there is a strong magnitude-distance trade-off in terms of damage and losses to the city, with smaller magnitude earthquakes on more local faults, in the magnitude range 6–7.5, producing 9 to 17 times more damage to the city and estimated fatalities compared to the great magnitude 8+ earthquakes located offshore on the subduction zone. Our calculations for this part of Chile show that unreinforced masonry structures are the most vulnerable to these types of earthquake shaking. We identify particularly vulnerable districts, such as Ñuñoa, Santiago and Macul, where targeted retrofitting campaigns would be most effective at reducing potential economic and human losses. Due to the potency of near-field earthquake sources demonstrated here, our work highlights the importance of also identifying and considering proximal minor active faults for cities in seismic zones globally, in addition to the more major distant large fault zones that are typically focused on in the assessment of hazard.

A Demonstrated System of Earthquake Emergency Auto-Handling Applied in Water Supply

In various kinds of natural disasters, earthquake is one of the most serious threats to the lifeline engineering systems. In the earthquake, except of the structure was destroyed, the function of the lifeline engineering systems was often subject to serious damages or totally loss, even caused fire or blood, or gave away poisonous gas and other series of major secondary disasters. To strengthen the function of the lifeline engineering and avoid or reduce the occurrence of secondary disasters, a demonstrated system of earthquake emergency auto-handling applied in water supply was built. The system was composed by the ED-1 type ground motion sensor module unit, the Panasonic FP-X C30R type PLC unit, The Kunlun Tongtai TPC7062K type unified touch screen unit and the multifunction water tower testing unit. The STA/LTA method and spectral intensity method were applied to deal with the distant earthquake and the near earthquake separately. Through theory and experiment analysis, the earthquake emergency auto-handling system could accurately measures the seismic records and performs the earthquake emergency auto-handling rapidly.

The geographical location of a distant earthquake

ABSTRACT Condensed from a paper published by the Geophysical Institute of the University of Zagreb (Ser. III, No. 8, 1957). C. Zeissig has given a graphical method for determining an epicenter by using direction lines which have been derived from the P times on pairs of stations. By a modified procedure it is possible—assuming an approximate value for the epicenter and the origin time—to draw the direction lines as straight lines on a large-scale map, whereby a preliminary condition for an accurate location of an earthquake is obtained. As the most probable epicenter there can be taken the center of gravity of selected intersection points of reliable direction lines. The selection itself is based on criteria which follow from a detailed study of the reliability of the lines and points. As an illustration of the method, a solution is given for one earthquake.