Hi, researchers,
When the volcano erupts, how to quickly measure the thickness of ash sediment by making an isopach map? Is any simple way to fast create the contour line of volcanic ash fall (tephra) deposit?
Welcome to any comments.
Hi Jie Dou...
Did you try use Surfer? it can create / generate map quickly.
Hi, Hasan Rosyadi,
Thanks for your comments
Maybe you do not understand my question. I know your answer that using the Surfer to create contour line. But the problem is that first how to measure the depth of volcanic ash, because we have only an observation point. We can not install many observation points due to the expensive equipments.
Regards,
Dou
If you only have one data point this is going to be impossible to constrain. How many do you have? There are papers out there about making isopach maps with very few data points, and you could look to invert fallout models (i.e. if you knew the column height and wind field),,
Do you have DEM for the area? Both pre-event and post-event? If yes, you can subtract the two DEM and get the depth of volcanic ash/tephra deposit that might have occurred. Please let me know what other information you have so that I might help you better!
Dear Tuba san,
Thanks for your suggestions.
We need to real time monitor the depth of ash when the volcano erupts covering the whole mountain. So we can not get the pre/pos-dem DEM in time. We have the height plume data. We need to develop some model to simulate the depth of ash fall. It is a bit challenging for me to use some numerical /physical models. Do you have more idea about this field to easily carry out this process?
Hi Dou, I will check the details and get back to you. I am sure there are some models to simulate plumes. I will check and reply, with more details.
Goodluck!
I assume you are trying to create a model that will predict volcanic ash thickness from plume height, wind direction and velocity, amount of ash coming out and time. Its not that hard to measure ash thickness so research recent volcanic eruptions that have that data and create your model. The trick is how to measure how much ash ejecta is coming out per hour.
Good luck
Dear Paul,
Thanks for your suggestion. As you mentioned, it is a real problem with uncertainty. Also we do not have data around the crater. We installed some measuring equipments but no data around vent, so it is can not directly the spatial interpolation. first we need to predicte ash data around crater, the problem is that how to predict the ash data around volcnaoice vent?
Hi Jie Dou
If you don't have the equipment (i.e. ashmeters) installed in the downwind direction of the plume, and not possibilities for going to the field and measuring tephra depths, I recommend you two ways:
1) If there is any population all around, you can request to the people to give you real time thicknesses in the base of pictures with objects of known size (e.g. a coin) via social media. You have to be careful they understand the procedure and not expose their own safety during the process. We applied this technique at the 2015 Calbuco eruption and we collected about 20 data points by this way (see Romero et al. 2016 JVGR for details). You will need about 20-24 field data to reach a confidence level on your isopach map. Not possible to do anything confident with less than 10 points.
2) If you are not able to request that data, you can use the free USGS Ash3D model. Just need an account. The model request you the volcano name, plume height, date, time and duration of the eruption. A DRE magma volume is requiered. However, if you don't know the volume, you can use the column height to indirectly estimate the volume discharge rate and then extrapolate it in time for reaching an erupted volume (see Mastin et al 2009 for equations, very easy). If not, you can suppose a volume from a similar eruption in other place of the world.The software gives to you an isopach map with kmz retrieves for unsing in Google Earth.
Hope this information is useful to you. Any question, do not hesitate to contact me.
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