Preprints
https://doi.org/10.5194/nhess-2024-110
https://doi.org/10.5194/nhess-2024-110
04 Jul 2024
 | 04 Jul 2024
Status: this preprint is currently under review for the journal NHESS.

Mid-field tsunami hazards in greater Karachi from seven hypothetical ruptures of the Makran subduction thrust

Haider Hasan, Hira Ashfaq Lodhi, Shoaib Ahmed, Shahrukh Khan, Adnan Rais, and Muhammad Masood Rafi

Abstract. New Makran simulations imply two generalized zones of mid-field tsunami hazard in greater Karachi. The simulations presuppose seven megathrust ruptures that strike east-west, range in area from 100 × 150 km to 355 × 800 km, and lie west of the city by no less than 100 km. The assumed seismic slip is uniform across each rupture area. The smallest rupture approximates the 1945 Makran earthquake of magnitude 8.1, while the largest corresponds to a previously conjectured giant Makran earthquake of magnitude 9.2. None of the sources include a complication in 1945: late-arriving waves from submarine slides or splay faulting. Consequently, the first simulated wave is the largest in each of the seven scenarios. And because the sources are to the west, the simulated waves are higher, and arrive sooner, at Karachi Port (1.5 hr) than 30 km farther east at Port Qasim (nearly 3 hr). These combinations of height and arrival time can be generalized as properties of two hazard zones: a western one that includes Karachi Port, and an eastern one that includes Port Qasim. The simulated flooding extends farthest inland into low-lying residential areas of the western zone. Neither hazard zone is near-field or far-field. That is, neither is near enough to the fault ruptures for felt seismic shaking to dependably warn of a fast-arriving tsunami, yet neither is distant enough to receive more than three hours of advance notice through tsunami warning systems. Our simulations are intended to support emergency management in this mid-field setting. 

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Haider Hasan, Hira Ashfaq Lodhi, Shoaib Ahmed, Shahrukh Khan, Adnan Rais, and Muhammad Masood Rafi

Status: open (until 15 Aug 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on nhess-2024-110', Amin Rashidi, 20 Jul 2024 reply
Haider Hasan, Hira Ashfaq Lodhi, Shoaib Ahmed, Shahrukh Khan, Adnan Rais, and Muhammad Masood Rafi
Haider Hasan, Hira Ashfaq Lodhi, Shoaib Ahmed, Shahrukh Khan, Adnan Rais, and Muhammad Masood Rafi

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Short summary
Our study models tsunami risks for Karachi, identifying two hazard zones with varying wave heights and arrival times. Karachi Port is at higher immediate risk. We conducted this research to understand the city's vulnerability to tsunamis from the Makran Subduction Zone and to improve emergency response plans. Using simulations of seven potential earthquake scenarios, we highlight the need for tailored disaster strategies and effective early warning systems to protect coastal communities.
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