A delegation from the Japanese city of Toyama has arrived in Christchurch to attend the Royal Commission's hearing into the collapse of the Canterbury Television (CTV) building.
The building housed a foreign language school and 13 students from the city died when it collapsed in the February 22, 2011 earthquake.
In total, 115 people died in the disaster.
Today, the inquiry heard how the soil under the Canterbury Television building was "soft" in the north-east corner.
Tim Sinclair, a chartered professional engineer for Tonkin & Taylor and an expert in foundation engineering, prepared and contributed to a report on the soil at the CTV site.
His findings were given to structural engineers Clark Hyland and Ashley Smith for their co-authored report to the Department of Building and Housing (DBH).
Sinclair said the interpretation of the soil under the CTV building in 1986 was that there was a "consistent'' gravel layer of about 4 metres across the site, with silt (sand) below.
Soil "stiffness'' was important for the resilience of the ground as well as its connection to the building above, he said.
However, he found in one area - what he called the north-east quadrant - the gravel was largely "absent''.
In one bore hole he drilled there was only about 100mm of gravel, then silt.
That meant the ground in that corner was softer, Sinclair said.
About 13 bore holes were drilled by machine and by hand on the CTV site for the building's construction.
In areas where the gravel did go down to four metres, Sinclair found some bore holes did not reach the silt below.
The inquiry has also been hearing evidence on whether a renovation of the building in April 2000 had an effect on its stability.
The re-fit included the construction of an internal staircase, which structural engineer David Falloon said was designed by a "fresh graduate".
Falloon said the plans for the staircase may have been lost after his office block was demolished post-quake.
Earlier the commission heard from Dr Brendon Bradley, director of Bradley Seismic and a lecturer in civil and natural resources engineering at Canterbury University.
Bradley said in spite of suggestions the CTV site was, by nature, particularly vulnerable to the vertical forces experienced during the February, it was in fact consistent with results seen in similar events elsewhere.
Based on the evidence to date, the vertical nature of the February 2011 quake was not "unique", Bradley said.
The inquiry has held 60 hearing days so far and more than 80 witnesses have been called.
The hearings into the CTV building collapse is now into its fifth week.