After the Quake: Defining ritual and earthquake proofing in monument foundations, Kathmandu Valley UNESCO World Heritage Site.

Overview

At the juncture of the Indian and Eurasian tectonic plates, earthquakes are a common and regular occurrence in Nepal with at least eight major earthquakes above magnitude 6.0 in the 20th and 21st century (Chaulagain et al., 2018; BCDP, 1994). The most recent Gorkha (Nepal) earthquake of 25th April 2015 (magnitude 7.8) and the associated series of aftershocks was a major catastrophe resulting in over 9,000 deaths, 20,000 injured and the destruction of 500,000 homes (USGS 2018; Coningham et al., 2016; Bilham 2015). Nepal’s historic monuments were also caught up in this catastrophe with 691 damaged, of which 131 collapsed causing death and injury, and which included the seven properties and monuments of the UNESCO Kathmandu Valley World Heritage Site (Bhagat et al, 2016; Davis et al., 2019). As well as their international cultural significance and contributions to local economies through tourism, vitally the Kathmandu Valley monuments are a living heritage bringing daily cohesion to the lives of thousands where people commune with guiding deities (Coningham et al., 2016). With future earthquakes inevitable and cultural imperatives imbued in these monuments, post-earthquake programmes of monument reconstruction and restoration within the Kathmandu Valley WHS seek to conserve cultural ‘universal values’ and ‘authenticities’ together with ‘earthquake proofing’ the monument for the future (UNESCO, 2019). The reconciling of these reconstruction objectives is brought into sharp focus when considering monument foundations.

Geologically Kathmandu Valley comprises a complex series of Pleistocene fluvio-lacustrine lake-bed sediments (gravels, sands, clays of varying strengths) making the Kathmandu Valley particularly sensitive to earthquake ground motion amplification, liquefaction and consequent building collapse (Simpson et al., 2019; Gautam, et al., 2017; Rajaura et al., 2017). To assess the sediments underlying monument superstructures our post 2015 earthquake salvaging of seven sites in the Kathmandu Valley (WHS) included excavation of foundations through to the underlying lake-bed sediments. Monument foundations can be up to 3m thick and comprise sequences of soils, sediments and brick walling with mortar (Davis et al., 2019; Simpson et al., 2019). On the basis of systematic field observation (Munsell colour, texture, structure, cultural inclusions, sediment property variances) it is evident that the foundations are fundamentally different in their composition compared to the underlying early lake-bed sediments and have been deliberately placed. Furthermore, there is little or no evidence at the field-scale of rip-up clasts, ‘bulbous’ stratigraphy horizon modifications, and dykes and sills normally evident in earthquake modified sediment fabrics although these features are found in sediments beyond the monument (Giona Bucci et al., 2018). Drawing on South Asian documentary sources from the 6th century (the Brhatsamhita) and the 11th Century (the Mayamata and Mansara) that give instructions on building architectures of religious buildings, the distinctiveness of monument foundations is further emphasised. Instructions within these ‘manuals’ include the selection of materials for foundations, the ways in which materials should be organised and deposited, and how the construction site should be managed from a ritual perspective. The foundations are therefore evidenced as of major cultural significance for the understanding of monument construction, and in the seismic Kathmandu Valley environment are buffers between underlying lake-bed sediments and monument superstructures. Beyond these observations the formation and function of these monument foundations are not currently understood.

Current geosciences and historically based readings of Kathmandu Valley heritage site foundations open a series of hypotheses that are of fundamental significance to understanding monument foundation constructions in seismic environments. These hypotheses include that: monument foundations in the Kathmandu Valley are a deliberately constructed deposition – an archaeo-sediment; there is a ritualistic dimension regulating selection of materials and foundation construction; the monument foundations are ‘earthquake proofed’ over extended periods of time as a result of these deliberate constructions; there is a common ‘recipe’ applied to the formation of monument foundations; and that historically there has been rebuilding of superstructures after earthquake events on foundations that have remained stable.

The programme of research has as its purpose the assessment of these hypotheses through an integrated geosciences-based stratigraphic analyses of foundation sections, calibrated against Kathmandu Valley sediment stratigraphies, from seven structurally and chronologically contrasting monuments within the Kathmandu Valley – at Pashupati, Patan, Bhaktapur, Changu Naryan, Jaisideval, Trialokya Mohan, and the Nine Storey Palace. These will include stratigraphically and geo-chronologically controlled assessments and analyses of bulk and undisturbed sediment samples. Addressing the hypotheses in this way will evidence the nature of the cultural significance associated with foundation sediments in and the Kathmandu Valley WHS monuments. The work will also fundamentally shape a balanced approach to post-earthquake reconstruction of heritage monuments in Kathmandu Valley and the wider South Asian region by determining where and when it is appropriate to make a case for embedding these traditional foundations within monument reconstructions both now and in the future.

Methodology

Field programme: The programme is COVID19 proofed as stratigraphies from selected sites have been logged, samples collected on a context and sub-context framework, transported and stored at the University of Stirling. New stratigraphic sections, are becoming available with fieldwork undertaken if COVID19 restrictions allow. We work closely with the Nepal Government Department of Archaeology (including GCRF programmes) who have competencies in geosciences sample collection.

Geochronologies: Optically stimulated luminescence measurements (OSL); local geology dose rates and stored doses in feldspars and quartz give dating control on foundation sediments and chronological range to the monuments considered. Based at CERSA Luminescence, University of St Andrews and Radioactivity laboratories, University of Stirling. Radiocarbon measurement of wooden superstructures gives comparison of superstructure age to foundation age. Based at SUERC, University of Glasgow.

Sediment analyses 1: Bulk sample analyses of particle size distributions, X-ray Diffraction of clays, Atterberg limits, soil strength (bulk densities and resistance). Interpreted as sediment indicators of ritual selections and earthquake susceptibility. Undertaken at the University of Stirling Environmental Science laboratories with placement at Historic Environment Scotland, Engine Shed Laboratories and in collaboration with Atkins Engineering.

Sediment analyses 2: Analyses of undisturbed samples by thin section micromorphology and image analyses with associated Scanning Electron Microscopy – Energy Dispersive X-Ray analyses (SEM-EDX). Interpreted as indicators of ritual selections and deposition characteristics together with the identification of phase histories of earthquake imprints on the sediments. Undertaken at the University of Stirling Micromorphology and Microscopy laboratories.

Project Timeline

Year 1

Geological and archaeological contextualisation reviews; stratigraphic sequencing across sites; OSL laboratory training; creation of geochronology framework from existing samples; first phase fieldwork.

Year 2

Second phase fieldwork; complete stratigraphic sequencing; complete geochronological frameworks, publish findings. Sediment 1 training and analyses; integrate ritual and earthquake proofing with heritage managers and geo-engineers, publish findings.

Year 3

Sediment 2 training and analyses; complete analyses of undisturbed samples assessing sediment architectures for ‘shadow’ earthquake imprints, publish findings; commence thesis write-up.

Year 3.5

Develop impact outcomes and communications for heritage managers and engineers; complete thesis write-up.

Training
& Skills

The studentship offers full training in advanced geoscience methods applied to archaeological site formation; these skills are transferable into a range of environmental, geological, archaeological and geo-engineering settings.

Training in archaeological contextualisation and synthesis is provided by Coningham at Durham. The student is granted access to the full suite of analytical laboratories for OSL at St Andrews; training is provided by Kinnaird. Full training is given in advanced sediment stratigraphy analyses of bulk samples by Simpson, Wilson, and Dr Callum Graham (Historic Environment Scotland) at Stirling. Training in thin section micromorphology analyses, associated SEM-EDX analyses and novel image analyses approaches to yield ‘shadow’ earth-quake imprints in sediments will be provided by Simpson and Wilson at Stirling.

References & further reading

Bilham, R. (2015). Raising Kathmandu. Nature Geoscience, 8(8), 582-584. https://doi.org/10.1038/ngeo2498.

Bhagat, S. et al., (2017). Damage to Cultural Heritage Structures and Buildings Due to the 2015 Nepal Gorkha Earthquake. Journal of Earthquake Engineering, 22(10), pp.1861-1880. DOI: https://doi.org/10.1080/13632469.2017.1309608

Building Code Development Project. (1994). Seismic hazard mapping and risk assessment for Nepal. Kathmandu: Ministry of Housing and Physical, Planning, Government of Nepal. (UNDP/UNCHS (Habitat) Subproject: NEP/88/054/21.03).

Chaulagain, H. et al. (2018). Chapter 1 – Revisiting Major Historical Earthquakes in Nepal: Overview of 1833, 1934, 1980, 1988, 2011, and 2015 Seismic Events. In: D. Gautam & H. Rodrigues, eds. Impacts and Insights of the Gorkha Earthquake. Netherlands: Elsevier, pp. 1-17. https://doi.org/10.1016/B978-0-12-812808-4.00001-8

Coningham, R. et al. (2016). Preliminary results of post-disaster archaeological investigations at the Kasthamandap and within Hanuman Dhoka, Kathmandu Valley UNESCO World Heritage Property (Nepal). Ancient Nepal, (191-192), pp. 28-51. http://dro.dur.ac.uk/19704/1/19704.pdf

Coningham, R. et al. (2019). Reducing disaster risk to life and livelihoods by evaluating the seismic safety of Kathmandu’s historic urban infrastructure: enabling an interdisciplinary pilot. Journal of the British Academy, 7(s2), 45-82. DOI: https://doi.org/10.5871/jba/007s2.045

Davis, C. et al. (2019). Identifying archaeological evidence of past earthquakes in a contemporary disaster scenario: case studies of damage, resilience and risk reduction from the 2015 Gorkha Earthquake and past seismic events within the Kathmandu Valley UNESCO World Heritage Property (Nepal). Journal of Seismology, 24(4), pp.729-751. https://doi.org/10.1007/s10950-019-09890-7

Gautam, D. et al. (2017). Soil liquefaction in Kathmandu valley due to 25 April 2015 Gorkha, Nepal earthquake. Soil Dynamics and Earthquake Engineering, 97, pp.37-47. DOI10.1016/j.soildyn.2017.03.001

Giona Bucci, M. et al. (2019), Micromorphological analysis of liquefaction features in alluvi-al and coastal environments of Christchurch, New Zealand. Sedimentology, 66, pp. 963-982. doi:10.1111/sed.12526

Rajaure, S. et al. (2017). Characterizing the Kathmandu Valley sediment response through strong motion recordings of the 2015 Gorkha earthquake sequence. Tectonophysics, 714-715, pp. 146-157, https://doi.org/10.1016/j.tecto.2016.09.030

Further Information

Ian A. Simpson

University of Stirling
i.a.simpson@stir.ac.uk
Tel: +44 (0)1786 467850
Mob: +44 07876 538600

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