Abstract
AbstractMajor faults of the Tien Shan, Central Asia, have long repeat times, but fail in large (7+) earthquakes. In addition, there may be smaller, buried faults off the major faults which are not properly characterized or even recognized as active. These all pose hazard to cities along the mountain range front such as Almaty, Kazakhstan. Here, we explore the seismic hazard and risk for Almaty from specific earthquake scenarios. We run three historical‐based earthquake scenarios (1887 Verny7.3, 1889 Chilik8.0 and 1911 Chon‐Kemin8.0) on the current population and four hypothetical scenarios for near‐field faulting. By making high‐resolution Digital Elevation Models (DEMs) from SPOT and Pleiades stereo optical satellite imagery, we identify fault splays near and under Almaty. We assess the feasibility of using DEMs to estimate city building heights, aiming to better constrain future exposure datasets. Both Pleiades and SPOT‐derived DEMs find accurate building heights of the majority of sampled buildings within error; Pleiades tri‐stereo estimates 80% of 15 building heights within one sigma and has the smallest average percentage difference to field‐measured heights (14%). A moderately sized6.5 earthquake rupture occurring on a blind thrust fault, under folding north of Almaty is the most damaging scenario explored here due to the modeled fault stretching under Almaty, with estimated 12,3005,000 completely damaged buildings, 4,1003,500 fatalities and an economic cost of 4,7002,700 Million US dollars (one sigma uncertainty). This highlights the importance of characterizing location, extent, geometry, and activity of small faults beneath cities.
Highlights
Earthquakes within the continental interiors of low and middle income countries pose the greatest earthquake risk worldwide to human life
The peak ground accelerations we calculate for Almaty (Figure S4) are very similar to those of Mosca et al (2019), in which Almaty likely experieEnced 0E.5–0.6g PGA for the Verny earthquakeE and 0E.3–0.4g
We compare building heights derived from high-resolution Digital Elevation Models (DEMs) with field measurements to see if DEMs can reliably estimate city building heights, and compare the relative accuracy of estimates derived from SPOT and Pleiades imagery, with a view to incorporating these into exposure models to help improve risk calculations in the future
Summary
Earthquakes within the continental interiors of low and middle income countries pose the greatest earthquake risk worldwide to human life. People living in economically developing countries are significantly more vulnerable to all hazards, including earthquakes (Schneiderbauer & Ehrlich, 2004) This lack of resilience can be due to knowledge factors; in contrast to plate boundaries, the faults are slow moving and hard to measure, and there is often AMEY ET AL. Smaller faults located near or under a city upon which much smaller earthquakes occur are likely to do much more damage due to proximity to the exposed urban population for example, Kobe 1E995 (MEw 6.9, 5,000 fataElities, 43,000 injuries [Yamazaki et al, 1996]), Bam 2E003 (Mw 6.6, 30,000 fatalities [England & Jackson, 2011]), Kashmir E2005 (Mw 7.6, 75,000 fatalities [England & Jackson, 2011]). This is a problem in rapidly developing regions, where cities expand onto faults, for example in Santiago, Chile (Hussain et al, 2020)
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