is it possible to access an element within array of array?

In your second loop, the b array is only half initialized (once for every even number from 1 to 10) so when you try to dereference b[5] you get undefined behavior and hence a segfault

It works fine until you get to i = 5 for the second loop. When i = 5, a[b[5]] is undefined because b[5] is uninitialized. After the first loop, you have b[] = {1, 3, 5, 7, 9, ....} the rest is uninitialized. Try to initialize b[10] and it should work.

b[10] = {};

This method should work:

a[b[i]];

I'm not 100% sure it will work though, because the compiler has a role to play here too. For example, it works perfectly in TC++...

A better way to do it is this:

for(i=0;i<10;i++)
{
    int temp=b[i];
    c[v]=a[temp];
    v++;
}

Here is the reason for the error you see:

'Segmentation fault' in this case means that you used a[] array index well beyond a value within memory available to the process (note: it does not need to be beyond the memory range of your computer to get this error; also note that using indexes slightly bigger than array size usually do not cause segmentation faults; but such index value is still a semantic error, of course).

When you declare b[], you do not initialize it (and that is usual). Your first loop only initializes selected elements of b[]: only as much elements from the beginning of b[], as there are even numbers in a[] (you use the condition:a[i]%2==0).

Currently, you have 5 even numbers in a: 2,4,6,8,10. This is sufficient to initialize elements of b[0]...b[4]. The elements of b[] starting with b[5] are left uninitialized, i.e. contain numbers which can be considered random, or trash. You can print b[5]...b[9] to see what do they contain without initialization – it is often 0’s (making debugging even harder, because a[0] does not cause segmentation faults - but a[0] is probably not what you want to get in c[]).

But in different runs of your program elements of b[] starting with b[5] can be anything (and then any of them can make a segmentation fault, e.g. a[-2000000000]).
Chances are extremely low that these accidental values will represent valid indexes of a[].

Relief: change your SECOND loop so it runs only k times, not 10 times. This was probably your initial intention, anyway: for(i=0;i<k;i++)

#include <iostream>
using namespace std;
int main()
{
    int k=0,v=0,i,b[10],c[10];
    int a[]={1,2,3,4,5,6,7,8,9,10};
    for(i=0;i<10;i++){
        if(a[i]%2==0) 
        {b[k]=i; k++;}
    }
    for(i=0;i<5;i++)
    {
        c[v]=a[b[i]];
        v++;
    }
    return 0;
}

works well