Context :

Aims : Previous literature suggests that the densest structures in the interstellar medium form through colliding flows , but patent evidence of this process is still missing .
Recent literature proposes using SiO line emission to trace low-velocity shocks associated with cloud formation through collision .
In this paper we investigate the bright and extended SiO ( 2–1 ) emission observed along the \sim 5 pc-long W43-MM1 ridge to determine its origin .

Methods : We used high angular resolution images of the SiO ( 2–1 ) and HCN ( 1–0 ) emission lines obtained with the IRAM plateau de Bure ( PdBI ) interferometer and combined with data from the IRAM 30 m radiotelescope .
These data were complemented by a Herschel column density map of the region .
We performed spectral analysis of SiO and HCN emission line profiles to identify protostellar outflows and spatially disentangle two velocity components associated with low- and high-velocity shocks .
Then , we compared the low-velocity shock component to a dedicated grid of one-dimensional ( 1D ) radiative shock models .

Results : We find that the SiO emission originates from a mixture of high-velocity shocks caused by bipolar outflows and low-velocity shocks .
Using SiO and HCN emission lines , we extract seven bipolar outflows associated with massive dense cores previously identified within the W43-MM1 mini-starburst cluster .
Comparing observations with dedicated Paris-Durham shock models constrains the velocity of the low-velocity shock component from 7 to 12 km.s ^ { -1 } .

Conclusions : The SiO arising from low-velocity shocks spreads along the complete length of the ridge .
Its contribution represents at least 45 % and up to 100 % of the total SiO emission depending on the area considered .
The low-velocity component of SiO is most likely associated with the ridge formation through colliding flows or cloud-cloud collision .